WO2016002613A1

WO2016002613A1 - Polishing liquid composition for magnetic disk substrates

Info

Publication number: WO2016002613A1
Application number: PCT/JP2015/068308
Authority: WO
Inventors: 木村陽介; 内野陽介
Original assignee: 花王株式会社
Priority date: 2014-06-30
Filing date: 2015-06-25
Publication date: 2016-01-07
Also published as: JP2016027517A; GB201511439D0; TW201610125A; MY184290A; JP5853117B1; GB2528386A; TWI586795B

Abstract

Provided is a method for producing a magnetic disk substrate, which is capable of reducing long-period defects on a substrate surface after lapping. According to one embodiment of the present invention, the production method comprises (1) a polishing step using a polishing liquid composition (I), (2) a step for cleaning the obtained substrate, and (3) a step for polishing the obtained substrate using a polishing liquid composition (II) that contains silica particles (C). The steps (1) and (3) are carried out by different polishing machines, and (i) the polishing liquid composition (I) contains non-spherical silica particles (A), spherical silica particles (B), an acid, an oxidant and water, (ii) the mass ratio (A/B) is from 80/20 to 99/1 (inclusive), and the total content of the silica particles (A) and (B) is more than 98.0% by mass, (iii) the non-spherical silica particles (A) have a ∆CV value of more than 0.0% but less than 10%, (iv) the non-spherical silica particles (A) have a particle diameter ratio (D1/D2) of from 2.00 to 4.00 (inclusive), (v) the spherical silica particles (B) have a volume average particle diameter (D1) of from 6.0 nm to 80.0 nm (inclusive), and (vi) the acid is a phosphoric acid, phosphonic acid or organic phosphonic acid.

Description

Polishing liquid composition for magnetic disk substrate

The present disclosure relates to a polishing liquid composition for a magnetic disk substrate, a method for polishing a magnetic disk substrate, and a method for manufacturing a magnetic disk substrate.

In recent years, magnetic disk drives have been reduced in size and capacity, and high recording density has been demanded. In order to increase the recording density, it is necessary to improve the detection sensitivity of the magnetic signal. In view of this, technical development is underway to further reduce the flying height of the magnetic head and reduce the unit recording area. For magnetic disk substrates, the smoothness and flatness are improved (reduction of surface roughness, waviness, and edge sagging) and surface defects are reduced (residual abrasive, Reduction of scratches, protrusions, pits, etc.) is strictly demanded. From the viewpoint of achieving both improvement in surface quality and productivity, such as smoother and less scratches, such a requirement, the hard disk substrate manufacturing method includes a multi-stage polishing method having two or more polishing steps. Often adopted. In general, in the final polishing step of the multi-stage polishing method, that is, the final polishing step, a polishing composition for finishing that contains colloidal silica particles in order to satisfy the requirements of reducing surface roughness and scratches such as scratches, protrusions, and pits. In the polishing step (also referred to as rough polishing step) prior to the final polishing step, a polishing liquid composition containing alumina particles is used from the viewpoint of improving productivity. However, when alumina particles are used as the abrasive, media drive defects may be caused by the piercing of the alumina particles into the substrate.

Therefore, a method of manufacturing a magnetic disk substrate that can reduce the sticking of particles to the substrate by using a polishing composition containing no alumina particles and using silica particles as abrasive grains in the rough polishing step has been proposed. (Patent Documents 1 and 2).

On the other hand, phosphoric acid or phosphonic acid may be used as the acid contained in the polishing composition (Patent Document 3).

Furthermore, in order to improve the polishing rate of silica particles, silica particles having a plurality of protrusions on the surface (Patent Document 4) and beaded silica particles (Patent Document 5) have been proposed.

JP 2014-29754 A JP 2012-29755 A JP 2003-147337 A JP 2013-121631 A JP 2001-11433 A

If a rough polishing process and a final polishing process that do not use alumina particles are employed in the polishing process of the magnetic disk substrate, residual alumina (for example, alumina adhesion, alumina sticking) can be eliminated, thereby reducing projection defects. However, it has been found that when a rough polishing process is performed with silica particles instead of alumina particles, a problem that long-period defects cannot be removed occurs. When the rough polishing process is performed with alumina particles, the problem of long-period defects generally does not occur. Since the removal rate of long-period defects has a high correlation with the substrate yield, further improvement of the removal rate of long-period defects is desired in the rough polishing process.

Patent Document 1 discloses that if rough polishing is performed using non-spherical silica particles defined by predetermined parameters as abrasive grains, the polishing time for rough polishing is greatly prolonged even when alumina particles are substantially not included. Disclosed is that long-wave waviness after rough polishing can be reduced without doing so. However, for long-period defects, further improvement in removal rate is desired.

Therefore, in one or a plurality of embodiments, the present disclosure reduces long-period defects on the substrate surface after rough polishing without significantly impairing the polishing speed in rough polishing using non-spherical silica particles as abrasive grains. Provided is a polishing composition for a magnetic disk substrate.

In one or a plurality of embodiments, the present disclosure includes a method of manufacturing a magnetic disk substrate,
(1) a step of polishing a surface to be polished of a substrate to be polished using the polishing liquid composition I;
(2) a step of cleaning the substrate obtained in step (1), and
(3) It has the process of grind | polishing the board | substrate obtained at the process (2) using the polishing liquid composition II containing the silica particle C, and the said process (1) and (3) are another polishing machines. Done
(I) The polishing liquid composition I in the step (1) contains non-spherical silica particles A, spherical silica particles B, an acid, an oxidizing agent, and water,
(Ii) In the polishing composition I in the step (1), the mass ratio A / B between the non-spherical silica particles A and the spherical silica particles B is 80/20 or more and 99/1 or less, and the entire silica particles The total content of non-spherical silica particles A and spherical silica particles B with respect to
(Iii) The non-spherical silica particle A has a ΔCV value of more than 0.0% and less than 10%,
(Iv) The particle diameter ratio (D1 / D2) of the volume average particle diameter (D1) determined by the dynamic light scattering method and the specific surface area converted particle diameter (D2) determined by the BET method of the non-spherical silica particles A is 2.00 or more and 4 .00 or less,
(V) The volume average particle diameter (D1) of the spherical silica particles B by a dynamic light scattering method is 6.0 nm or more and 80.0 nm or less,
(Vi) The present invention relates to a method for producing a magnetic disk substrate, wherein the acid is at least one selected from the group consisting of phosphoric acids, phosphonic acids, organic phosphonic acids, and combinations thereof.

In one or a plurality of embodiments, the present disclosure relates to a magnetic disk substrate polishing method including steps (1) to (3) in the method of manufacturing a magnetic disk substrate according to the present disclosure.

In one or a plurality of embodiments, the present disclosure is a first polishing machine that performs the polishing in the step (1) in the method for manufacturing a magnetic disk substrate according to the present disclosure, and a step in the method for manufacturing the magnetic disk substrate according to the present disclosure. The present invention relates to a magnetic disk substrate polishing system comprising: a cleaning unit that performs the cleaning in (2); and a second polishing machine that performs polishing in step (3) in the method for manufacturing a magnetic disk substrate according to the present disclosure.

In one or a plurality of embodiments, the present disclosure is a polishing liquid composition for a magnetic disk substrate, comprising:
Containing abrasive grains, acid, oxidant and water,
The abrasive contains non-spherical silica particles A and spherical silica particles B,
The mass ratio A / B between the non-spherical silica particles A and the spherical silica particles B is 80/20 or more and 99/1 or less,
The non-spherical silica particle A has a ΔCV value of more than 0.0% and less than 10%,
CV90 of the non-spherical silica particles A is 20.0% or more and 40.0% or less,
The ΔCV value of the spherical silica particles B is higher than 0% and 10% or lower, and the CV90 of the spherical silica B is 10.0% or higher and 35.0% or lower,
The particle diameter ratio (D1 / D2) of the volume average particle diameter (D1) by the dynamic light scattering method of the non-spherical silica particles A to the specific surface area conversion particle diameter (D2) by the BET method is 2.00 or more and 4.00 or less. And
The volume average particle diameter (D1) of the spherical silica particles B by a dynamic light scattering method is 6.0 nm or more and 80.0 nm or less,
The present invention relates to a polishing composition for a magnetic disk substrate, wherein the acid is at least one selected from the group consisting of phosphoric acids, phosphonic acids, organic phosphonic acids, and combinations thereof.

The method for manufacturing a magnetic disk substrate according to the present disclosure does not use alumina particles, and thus can greatly reduce protrusion defects after rough polishing and after final polishing. According to the method for manufacturing a magnetic disk substrate according to the present disclosure, in one or a plurality of embodiments, the effect of reducing long-period defects on the substrate surface after rough polishing without significantly impairing the polishing rate in rough polishing. The substrate yield can be improved while maintaining the productivity of the substrate.

FIG. 1 is an example of an electron microscope (TEM) observation photograph of deformed colloidal silica abrasive grains. FIG. 2 is an example of an electron microscope (TEM) observation photograph of a confetti-type colloidal silica abrasive grain. FIG. 3 is a graph showing the volume particle size distribution. FIG. 4 is an example of a result obtained by measuring a substrate surface having a long-period defect (PED) with an optical interference type surface shape measuring machine. FIG. 5 is a diagram illustrating an embodiment of a polishing system. FIG. 6 is a diagram for explaining an embodiment of a polishing process of a method for manufacturing a magnetic disk substrate.

The present disclosure uses a predetermined acid (phosphoric acid or phosphonic acid) in the polishing liquid composition in a rough polishing step using a polishing liquid composition containing predetermined non-spherical silica particles and spherical silica particles as abrasive grains. Then, it is based on the knowledge that the removal rate of long-period defects is improved and the polishing rate is not greatly impaired. Generally, in the manufacture of a magnetic disk substrate, if long-period defects can be reduced, the substrate yield is improved. Therefore, according to the present disclosure, in one or a plurality of embodiments, the substrate yield can be improved while maintaining the productivity in the manufacture of the magnetic disk substrate.

The details of the mechanism by which the removal rate of long-period defects is improved without significantly impairing the polishing rate by the combination of the predetermined non-spherical silica particles and the spherical silica particles and the predetermined acid are not clear, but are assumed as follows. . That is, the non-spherical silica particles have more voids in the filled state than the spherical silica particles because of the surface shape. If particles of a specific size that enter this void are blended, in a mixed system containing a plurality of abrasive components, the filling rate of the abrasive particles is further increased, and the frictional resistance peculiar to non-spherical silica particles during polishing is alleviated. Therefore, it is estimated that the removal rate of long-period defects can be improved. And, it is considered that the polishing rate can be maintained or improved because the filling ratio of the abrasive grains increases or the cutting area on the substrate increases or the load applied during polishing is more easily transmitted to the substrate. Furthermore, the presence of phosphoric acid or phosphonic acid in the polishing composition makes it possible to reduce long-period defects, particularly PED (polish enhanced defect), with a small amount of polishing due to the corrosion inhibition effect of phosphoric acid or phosphonic acid. It is thought to improve. That is, the polishing rate is improved by using silica having a specific shape, and defects are suppressed by using a specific acid such as phosphoric acid, thereby achieving high quality of the substrate to be polished. In addition, as an advantage in terms of the polishing process, the polishing composition can act on the substrate more efficiently by using abrasives with a high filling rate and using a specific acid having a corrosion-inhibiting effect. It is conceivable that the supply amount of the liquid composition can be reduced as compared with the conventional one. However, the present disclosure need not be construed as being limited to these mechanisms.

That is, the present disclosure is, in one aspect, a method of manufacturing a magnetic disk substrate,
(1) a step of polishing a surface to be polished of a substrate to be polished using the polishing liquid composition I;
(2) a step of cleaning the substrate obtained in step (1), and
(3) It has the process of grind | polishing the board | substrate obtained at the process (2) using the polishing liquid composition II containing the silica particle C, and the said process (1) and (3) are another polishing machines. Done
(I) The polishing liquid composition I in the step (1) contains non-spherical silica particles A, spherical silica particles B, an acid, an oxidizing agent, and water,
(Ii) In the polishing composition I in the step (1), the mass ratio (A / B) of the non-spherical silica particles A and the spherical silica particles B is 80/20 or more and 99/1 or less, and silica The total content of the non-spherical silica particles A and the spherical silica particles B with respect to the whole particles exceeds 98.0% by mass,
(Iii) The non-spherical silica particle A has a ΔCV value of more than 0.0% and less than 10%,
(Iv) The particle diameter ratio (D1 / D2) of the volume average particle diameter (D1) determined by the dynamic light scattering method and the specific surface area converted particle diameter (D2) determined by the BET method of the non-spherical silica particles A is 2.00 or more and 4 .00 or less,
(V) The volume average particle diameter (D1) of the spherical silica particles B by a dynamic light scattering method is 6.0 nm or more and 80.0 nm or less,
(Vi) A method for manufacturing a magnetic disk substrate (hereinafter referred to as “manufacturing method according to the present disclosure”), wherein the acid is at least one selected from the group consisting of phosphoric acids, phosphonic acids, organic phosphonic acids, and combinations thereof. "). According to the manufacturing method according to the present disclosure, in one or a plurality of embodiments, protrusion defects after finish polishing can be significantly reduced without greatly impairing the polishing rate in rough polishing, and the surface of the substrate after rough polishing can be reduced. An effect that long-period defects can be reduced can be achieved.

In the present disclosure, the “long-period defect” includes PED (polish-enhanced-defect) and grind scratches generated in the manufacturing process of the Ni—P plated aluminum substrate. PED is an annealing step in the step of forming a plating film on an aluminum substrate, and refers to a portion of insufficient annealing caused by water or foreign matter adhering to the substrate surface. Grind scratches refer to grinding marks on a grindstone in a process of grinding an aluminum substrate before plating (grinding process). In one or a plurality of embodiments, the long-period defect and its removal rate can be measured using the measuring device described in the examples.

In the present disclosure, the “protrusion defect” mainly refers to a defect on the surface of the substrate that is considered to be derived from residual abrasive grains, abrasive grain adhesion, and abrasive sticking after the rough polishing process and the final polishing process. The protrusion defect on the substrate surface can be evaluated by a surface defect inspection apparatus such as microscopic observation or scanning electron microscope observation of the substrate surface obtained after polishing, and can be specifically evaluated by the method described in the examples. .

[Non-spherical silica particles A]
The polishing composition I used in the step (1) contains non-spherical silica particles A as described above. In one or a plurality of embodiments, examples of the non-spherical silica particles A include colloidal silica, fumed silica, and surface-modified silica. From the viewpoint of reducing long-period defects without significantly impairing the polishing rate, the non-spherical silica particles A are preferably colloidal silica, and more preferably colloidal silica having the following specific shape. The non-spherical silica particles A may be produced by a flame melting method or a sol-gel method from the viewpoint of reducing long-period defects without significantly reducing the polishing rate. Preferably there is.

[Shape of non-spherical silica particle A]
The shape of the non-spherical silica particles A is a shape in which a plurality of particles (for example, two or more particles) are aggregated or fused from the viewpoint of reducing long-period defects without significantly impairing the polishing rate. In one or a plurality of embodiments, the non-spherical silica particles A are selected from the group consisting of confetti-type silica particles A1, deformed-type silica particles A2, and deformed and confetti-type silica particles A3. At least one type of silica particles is preferable, and irregular-shaped silica particles A2 are more preferable.

In the present disclosure, the confetti-type silica particle A1 refers to a silica particle having unique ridge-like protrusions on the spherical particle surface in one or a plurality of embodiments (see FIG. 2). In one or a plurality of embodiments, the silica particle A1 has a shape in which two or more particles different in particle size by 5 times or more are aggregated or fused on the basis of the particle size of the smallest silica particle. Preferably, particles having a small particle size are partially embedded in particles having a large particle size. The particle diameter can be obtained as the equivalent circle diameter measured in one particle in an electron microscope (TEM or the like) observation image, that is, the major axis of an equivalent circle having the same area as the projected area of the particle. The particle diameter in silica particle A2 and silica particle A3 can be similarly determined.

In the present disclosure, the irregular-shaped silica particle A2 refers to a silica particle having a shape in which two or more particles, preferably 2 to 10 particles are aggregated or fused (see FIG. 1). In one or a plurality of embodiments, the silica particle A2 has a shape in which two or more particles having a particle size of 1.5 times or less are aggregated or fused on the basis of the particle size of the smallest silica particle.

In the present disclosure, the irregular and confetti-type silica particles A3 are particles having a shape in which two or more particles are aggregated or fused. In one or a plurality of embodiments, the silica particle A3 is a particle obtained by agglomerating or fusing two or more particles having a particle size of 1.5 times or less, and further having the smallest agglomerated or fused silica particle. In this shape, small particles having a particle size of 1/5 or less are aggregated or fused.

In one or more embodiments, the non-spherical silica particle A is any one of the silica particles A1, A2, and A3, any two of the silica particles A1, A2, and A3, or the silica particles A1, A2, and Includes all of A3. The proportion (content) occupied by the total of silica particles A1, A2, and A3 in non-spherical silica particles A is preferably 50% by mass or more from the viewpoint of reducing long-period defects without significantly impairing the polishing rate. More preferably, it is 70 mass% or more, More preferably, it is 80 mass% or more, Still more preferably, it is 90 mass% or more or substantially 100 mass%.

[ΔCV value of non-spherical silica particle A]
In one or a plurality of embodiments, the ΔCV value of the non-spherical silica particles A is preferably higher than 0.0%, more preferably from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. It is 0.2% or more, more preferably 0.3% or more, still more preferably 0.4% or more. In one or a plurality of embodiments, the ΔCV value of the non-spherical silica particles A is preferably less than 10.0%, more preferably 8.0% or less, still more preferably 7.0% from the same viewpoint. Hereinafter, it is still more preferably 4.0% or less. In one or a plurality of embodiments, the ΔCV value of the non-spherical silica particles A is preferably more than 0.0% and less than 10.0%, more preferably 0.2% or more and 8.0% or less from the same viewpoint. More preferably, it is 0.3% or more and 7.0% or less, and still more preferably 0.4% or more and 4.0% or less.

In the present disclosure, the ΔCV value of the silica particles is the standard deviation of the particle diameter measured based on the scattering intensity distribution at the detection angle of 30 ° (forward scattering) by the dynamic light scattering method, and the detection angle of 30 ° by the dynamic light scattering. Measured based on the coefficient of variation (CV30) multiplied by 100 divided by the average particle size measured based on the scattering intensity distribution and the scattering intensity distribution at a detection angle of 90 ° (side scattering) by the dynamic light scattering method. The difference (ΔCV) from the value of the coefficient of variation (CV90) multiplied by 100 by dividing the standard deviation of the measured particle diameter by the average particle diameter measured based on the scattering intensity distribution at a detection angle of 90 ° by dynamic light scattering = CV30−CV90), which is a value indicating the angular dependence of the scattering intensity distribution measured by the dynamic light scattering method. The ΔCV value can be specifically measured by the method described in the examples.

The present inventor, as a method for showing the characteristics of non-spherical silica particles, the average particle size (D1) described above, the average particle size (D1) measured by the dynamic light scattering method and the specific surface area converted particle size by the BET method It was thought that the polishing performance of the silica particles could not be expressed only by the conventional view expressed using the particle size ratio (D1 / D2) with (D2). According to further studies by the present inventors, the ΔCV value is effective as a means for knowing the state of the entire system (bulk) of non-spherical silica particles, and by focusing on these parameters, polishing that has not been known in the past It has been found that the reduction in speed is suppressed, the removal rate of long-period defects is improved, and the range of non-spherical silica that can reduce protrusion defects can be accurately defined. That is, the non-spherical silica particles have different ΔCV values depending on the degree of irregularity, and the ΔCV value can be an index indicating the degree of irregularity of the non-spherical silica particles. For example, when the degree of irregularity of non-spherical silica particles increases, pseudo multiple scattering (self-scattering) is likely to occur, and the angle dependency of the scattering intensity distribution measured by the dynamic light scattering method decreases and the ΔCV value decreases. .

In the present disclosure, “scattering intensity distribution” means three particle size distributions (scattering) of sub-micron or less particles obtained by dynamic light scattering (DLS: Dynamic LightcScattering) or quasielastic light scattering (QLS). The particle size distribution of the scattering intensity among the intensity, volume conversion, and number conversion.

[Volume average particle diameter of non-spherical silica particle A by dynamic light scattering method (D1)]
The volume average particle diameter (D1) of the non-spherical silica particles A is preferably 120.0 nm or more and less than 300.0 nm in one or a plurality of embodiments from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. . In one or a plurality of embodiments, the volume average particle diameter (D1) of the non-spherical silica particles A is preferably 120.0 nm or more, more preferably 150.0 nm or more, and further preferably 160.0 nm or more, from the same viewpoint. Even more preferably, it is 170.0 nm or more, still more preferably 180.0 nm or more, still more preferably 190.0 nm or more, and even more preferably 200.0 nm or more. In one or a plurality of embodiments, the volume average particle diameter (D1) of the non-spherical silica particles A is preferably less than 300.0 nm, more preferably less than 260.0 nm, and still more preferably less than 250.0 nm, from the same viewpoint. Even more preferably less than 220.0 nm, even more preferably less than 210.0 nm. In one or a plurality of embodiments, the volume average particle diameter (D1) of the non-spherical silica particles A is preferably 120.0 nm or more and less than 260.0 nm, more preferably 150.0 nm or more and less than 260.0 nm, from the same viewpoint. More preferably 160.0 nm or more and less than 260.0 nm, even more preferably 170.0 nm or more and less than 260.0 nm, even more preferably 180.0 nm or more and less than 250.0 nm, even more preferably 190.0 nm or more and 220.0 nm. Is more preferably 200.0 nm or more and less than 210.0 nm.

In the present disclosure, the volume average particle diameter (D1) of silica particles refers to an average particle diameter based on a scattering intensity distribution measured by a dynamic light scattering method, and unless otherwise specified, the average particle diameter of silica particles is The average particle diameter based on the scattering intensity distribution measured at a detection angle of 90 ° in the dynamic light scattering method. The volume average particle diameter (D1) of the silica particles in the present disclosure can be specifically obtained by the method described in the examples.

[Particle size ratio of non-spherical silica particles A (D1 / D2)]
The particle diameter ratio (D1 / D2) of the volume average particle diameter (D1) by the dynamic light scattering method of the non-spherical silica particles A and the specific surface area converted particle diameter (D2) by the BET method is as follows: From the viewpoint of suppressing a decrease in the polishing rate and improving the long-period defect removal rate, 2.00 or more is preferable, more preferably 2.50 or more, still more preferably 3.00 or more, and even more preferably 3.50 or more. . In one or more embodiments, the particle diameter ratio (D1 / D2) of the non-spherical silica particles A is preferably 4.00 or less, more preferably 3.90 or less, and still more preferably 3.80, from the same viewpoint. It is as follows. In one or more embodiments, the particle diameter ratio (D1 / D2) of the non-spherical silica particles A is preferably 2.00 or more and 4.00 or less, more preferably 2.50 or more and 3.90, from the same viewpoint. Hereinafter, it is more preferably from 3.00 to 3.90, and even more preferably from 3.50 to 3.80.

In the present disclosure, the specific surface area equivalent particle size (D2) of the silica particles is given by the formula of D2 = 2720 / S [nm] from the specific surface area Sm ² / g measured by the nitrogen adsorption method (BET method).

The particle diameter ratio (D1 / D2) between the volume average particle diameter (D1) measured by the dynamic light scattering method and the specific surface area converted particle diameter (D2) by the BET method may mean the degree of deformation of the silica particles A. . In general, the volume average particle diameter (D1) measured by the dynamic light scattering method is such that when the silica particles are irregularly shaped particles, the processing is performed by detecting light scattering in the long direction. Considering the length, the larger the degree of deformation, the larger the value. The specific surface area equivalent particle diameter (D2) by the BET method is expressed as a sphere on the basis of the volume of the obtained particle, and is a smaller numerical value than D1. From the viewpoint of polishing rate, the particle size ratio (D1 / D2) is preferably large in the above range.

[CV90 of non-spherical silica particle A]
In one or a plurality of embodiments, the CV90 of the non-spherical silica particles A is preferably 20.0% or more, more preferably 25.0% or more, from the viewpoint of suppressing a decrease in polishing rate and improving the long-period defect removal rate. Further, it is preferably 27.0% or more, and from the same viewpoint, it is preferably 40.0% or less, more preferably 38.0% or less, still more preferably 35.0% or less, and even more preferably 32. 0.0% or less. In one or a plurality of embodiments, the CV90 of the non-spherical silica particle A is 20.0% or more and 40.0% or less, preferably 25.0% or more and 38.0% or less, from the same viewpoint. Preferably they are 25.0% or more and 35.0% or less, More preferably, they are 27.0% or more and 32.0% or less.

In the present disclosure, CV90 of silica particles is a coefficient of variation obtained by dividing the standard deviation based on the scattering intensity distribution by the average particle diameter and multiplying by 100 in the dynamic light scattering method, and has a detection angle of 90 ° (side scatter). ) Is the CV value measured. Specifically, CV90 of silica particles A can be obtained by the method described in the examples.

[CV30 of non-spherical silica particle A]
The CV30 of the non-spherical silica particles A is a preferable range similar to the range indicated by the CV90. In short, it is appropriately set within a range that maintains the relationship with the ΔCV value (= CV30−CV90).

[Content of Nonspherical Silica Particle A in Polishing Liquid Composition I]
In one or a plurality of embodiments, the content of the non-spherical silica particles A in the polishing composition I is preferably 0.1% by mass or more from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. 0.5 mass% or more is more preferable, 1 mass% or more is still more preferable, and 2 mass% or more is still more preferable. From the economical viewpoint, the content is preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less, and even more preferably 15% by mass or less. In one or a plurality of embodiments, the content of the non-spherical silica particles A in the polishing liquid composition I is 0.1 from the viewpoint of suppressing the reduction of the polishing rate, improving the long-period defect removal rate, and economically. The mass is preferably from 30% by mass to 30% by mass, more preferably from 0.5% by mass to 25% by mass, further preferably from 1% by mass to 20% by mass, and still more preferably from 2% by mass to 15% by mass.

[Method for producing non-spherical silica particle A]
The non-spherical silica particles A were produced by a flame melting method, a sol-gel method, and a pulverization method from the viewpoint of suppressing a decrease in polishing rate in rough polishing, removing a long-period defect, and reducing protrusion defects after rough polishing and final polishing. It is preferably a silica particle produced by a water glass method (particle growth method using an alkali silicate aqueous solution as a starting material). The usage form of the non-spherical silica particles A is preferably a slurry.

The silica particles are usually 1) A mixture (seed liquid) of No. 3 sodium silicate of less than 10% by mass and seed particles (small-size silica) is put in a reaction vessel, and the seed liquid is heated to 60 ° C. or more for aging. 2) An acidic active silicic acid aqueous solution prepared by passing No. 3 silicate through a cation exchange resin and an alkali (alkali metal or quaternary ammonium) are dropped into the seed solution to make the pH constant. 3) It is obtained by growing spherical particles (seed particles) and 3) concentrating the mixed solution in the reaction vessel by aging after evaporation or by ultrafiltration (for example, Japanese Patent Application Laid-Open No. 47-1964, Japanese Patent Publication) No. 1-223412, Japanese Patent Publication No. 4-55125, Japanese Patent Publication No. 4-55127). However, it is often reported that non-spherical silica particles A can be produced if the steps are slightly changed in the same production process. For example, since active silicic acid is very chemically unstable, a slender silica sol can be produced by intentionally adding polyvalent metal ions such as Ca and Mg into the mixed solution in the reaction vessel. Furthermore, the temperature of the reaction product (mixed solution in the reaction vessel) (when the liquid temperature exceeds the boiling point of water, the water in the mixed solution evaporates and silica is dried at the gas-liquid interface), and the pH of the reaction product (mixing When the pH of the liquid is 9 or less, silica particles are liable to be linked), SiO ₂ / M ₂ O (M is an alkali metal or quaternary ammonium) in the reaction product, and a molar ratio thereof (at a molar ratio of 30 to 60, Non-spherical silica particles can be produced by changing (for example, non-spherical silica is selectively produced) (for example, Japanese Patent Publication No. 8-5657, Japanese Patent No. 2803134, Japanese Patent Application Laid-Open No. 2003-133267, Japanese Patent Application Laid-Open No. 2003-133267). 2006-80406, JP 2007-153671, JP 2009-137771, JP 2009-149493, 2011-16702). However, the manufacturing method of the non-spherical silica particle A is limited to these and is not interpreted.

The method of adjusting the particle size distribution of the non-spherical silica particles A is not particularly limited, but a method of giving a desired particle size distribution by adding particles serving as new nuclei in the process of particle growth in the production stage, Examples thereof include a method of mixing two or more types of silica particles having different particle size distributions so as to have a desired particle size distribution.

[Spherical silica particles B]
The polishing liquid composition I used in the step (1) contains spherical silica particles B as described above. In one or a plurality of embodiments, examples of the spherical silica particles B include colloidal silica, fumed silica, and surface-modified silica. The spherical silica particles B are preferably colloidal silica from the viewpoint of suppressing a decrease in polishing rate, improving the long-period defect removal rate, and reducing protrusion defects.

In one or more embodiments of the present disclosure, in one or a plurality of embodiments, spherical particles close to a true sphere can be used from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. Those having a sphericity of 0.9 to 1.1 can be used. The “spherical silica particles” may correspond to generally commercially available colloidal silica in one or more embodiments.

In one or a plurality of embodiments, the spherical silica particles B may be one kind of spherical silica particles or a combination of two or more kinds of spherical silica particles. When the spherical silica particles B are a combination of two or more types of spherical silica particles, in one or more embodiments, each spherical silica particle meets the requirements for “spherical silica particles B” described in this disclosure. Fulfill. In one or a plurality of embodiments, the spherical silica particles B are preferably two or more types having different particle diameters from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate.

[ΔCV value of spherical silica particles B]
In one or a plurality of embodiments, the ΔCV value of the spherical silica particles B is preferably higher than 0.0%, more preferably 0, from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. .2% or more, more preferably 0.3% or more, and still more preferably 0.4% or more. In one or a plurality of embodiments, the ΔCV value of the spherical silica particles B is preferably 10% or less, more preferably less than 10.0%, still more preferably 8.0% or less, and still more preferably from the same viewpoint. 7.0% or less, still more preferably 4.0% or less. In one or more embodiments, the ΔCV value of the spherical silica particles B is preferably more than 0.0% and less than 10%, more preferably more than 0.0% and less than 10.0% from the same viewpoint. More preferably, it is 0.2% or more and 8.0% or less, still more preferably 0.3% or more and 7.0% or less, and still more preferably 0.4% or more and 4.0% or less.

[Volume average particle diameter of spherical silica particle B by dynamic light scattering method (D1)]
The volume average particle diameter (D1) of the spherical silica particles B is 6.0 nm or more and 80.0 nm or less from the viewpoint of suppressing a decrease in the polishing rate and improving the long-period defect removal rate. In one or a plurality of embodiments, the volume average particle diameter (D1) of the spherical silica particles B is 6.0 nm or more, preferably 7.0 nm or more, from the same viewpoint. In one or a plurality of embodiments, the volume average particle diameter (D1) of the spherical silica particles B is 80.0 nm or less, preferably 70.0 nm or less, more preferably 60.0 nm or less, from the same viewpoint. is there. In one or a plurality of embodiments, the volume average particle diameter (D1) of the spherical silica particles B is 6.0 nm or more and 80.0 nm or less, preferably 6.0 nm or more and 70.0 nm or less, from the same viewpoint. More preferably, it is 7.0 nm or more and 60.0 nm or less.

As described above, the spherical silica particles B contained in the polishing liquid composition I are, in one or a plurality of embodiments, two types having different particle diameters from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. It is preferable to use larger particles. In one or a plurality of embodiments that are not limited as two types of combinations, the volume average particle diameter (D1) is a spherical particle having a particle size of 6.0 nm to 15.0 nm and a spherical particle having a particle size of 15.5 nm to 70.0 nm. A combination or a combination of spherical particles of 15.5 nm to 30.0 nm and spherical particles of 30.5 nm to 70.0 nm may be mentioned.

[Particle size ratio of spherical silica particles B (D1 / D2)]
The particle size ratio (D1 / D2) of the volume average particle size (D1) by the dynamic light scattering method of the spherical silica particles B and the specific surface area equivalent particle size (D2) by the BET method is determined in one or a plurality of embodiments. From the viewpoint of suppressing the decrease in speed and improving the long-period defect removal rate, it is preferably 1.00 or more, more preferably 1.10 or more, and still more preferably 1.15 or more. In one or a plurality of embodiments, the particle diameter ratio (D1 / D2) of the spherical silica particles B is preferably 1.50 or less, more preferably 1.40 or less, and still more preferably 1.30 or less, from the same viewpoint. It is. In one or more embodiments, the particle size ratio (D1 / D2) of the spherical silica particles B is 1.00 or more and 1.50 or less, preferably 1.10 or more and 1.40 or less, from the same viewpoint. More preferably, it is 1.15 or more and 1.30 or less.

[CV90 of spherical silica particles B]
In one or a plurality of embodiments, the CV90 of the spherical silica particles B is preferably 10.0% or more, more preferably 15.0% or more, from the viewpoint of suppressing reduction in polishing rate and improving the long-period defect removal rate. More preferably, it is 20.0% or more, and from the same viewpoint, it is preferably 35.0% or less, more preferably 32.0% or less, still more preferably 30.0% or less. In one or a plurality of embodiments, the CV90 of the spherical silica particles B is 10.0% or more and 35.0% or less, preferably 15.0% or more and 32.0% or less, more preferably, from the same viewpoint. Is 20.0% or more and 30.0% or less.

[Content of spherical silica particles B in polishing liquid composition I]
In one or more embodiments, the content of the spherical silica particles B in the polishing liquid composition I is preferably 0.01% by mass or more from the viewpoint of suppressing the reduction of the polishing rate and improving the long-period defect removal rate. 0.05 mass% or more is more preferable, 0.1 mass% or more is still more preferable, and 0.2 mass% or more is still more preferable. From the economical viewpoint, the content is preferably 3% by mass or less, more preferably 2.5% by mass or less, still more preferably 2% by mass or less, and even more preferably 1.5% by mass or less.

[Method for producing spherical silica particle B]
Spherical silica particles B are produced by the flame melting method, the sol-gel method, and the pulverization method from the viewpoint of suppressing the decrease in the polishing rate in the rough polishing, removing the long-period defects, and reducing the protrusion defects after the rough polishing and the final polishing. Rather, silica particles produced by a particle growth method using an alkali silicate aqueous solution as a starting material are preferable. The usage form of the spherical silica particles B is preferably a slurry.

[Frequency of volume particle size distribution of non-spherical silica particles A and spherical silica particles B]
The total overlap frequency of the volume particle size distributions of the non-spherical silica particles A and the spherical silica particles B in the polishing liquid composition I is the reduction of the polishing rate and the improvement of the long-period defect removal rate in one or more embodiments. From the viewpoint, 0% to 50% is preferable, more preferably 10% to 45%, still more preferably 15% to 40%, and still more preferably 20% to 35%. The overlapping frequency of the volume particle size distribution of the non-spherical silica particles A and the spherical silica particles B can be specifically obtained by the method described in the examples. It is presumed that the above-described effect occurs when the porosity and the small particles existing in the voids are appropriately balanced in the silica particle mixture having different sizes.

[Mass ratio of non-spherical silica particles A and spherical silica particles B in polishing liquid composition I]
The mass ratio (A / B), which is the ratio of the content of the non-spherical silica particles A and the spherical silica particles B in the polishing liquid composition I, is one or more embodiments. From the viewpoint of improving the removal rate, it is 80/20 or more, preferably 85/15 or more, more preferably 88/12 or more. In one or a plurality of embodiments, the mass ratio (A / B) of the non-spherical silica particles A and the spherical silica particles B is 99/1 or less, preferably 95/5 or less, more preferably. Is 92/8 or less. When the spherical silica particles B are a combination of two or more types of spherical silica particles, the content of the spherical silica particles B refers to the total content thereof. The same applies to the content of non-spherical silica particles A.

[Content of Other Silica Particles in Polishing Liquid Composition I]
In one or a plurality of embodiments, when the polishing liquid composition I contains silica particles in addition to the non-spherical silica particles A and the spherical silica particles B, the non-spherical silica particles A with respect to the entire silica particles in the polishing liquid composition I The total content of the spherical silica particles B exceeds 98.0% by mass, preferably 98.5% by mass or more, and more preferably 99.99% by mass, from the viewpoint of suppressing a decrease in the polishing rate and improving the long-period defect removal rate. It is 0% by mass or more, more preferably 99.5% by mass or more, still more preferably 99.8% by mass or more, and still more preferably substantially 100% by mass.

[acid]
The polishing liquid composition I contains at least one acid selected from the group consisting of phosphoric acids, phosphonic acids, organic phosphonic acids, and combinations thereof from the viewpoint of reducing long-period defects without significantly impairing the polishing rate. Containing. The use of an acid in the polishing liquid composition I includes the use of an acid and / or a salt thereof.

In the present disclosure, “phosphoric acids” refers to phosphoric acid and other similar compounds having a phosphoric acid skeleton. In one or a plurality of embodiments, pyrophosphoric acid is mentioned as the group of similar compounds. In the present disclosure, unless otherwise specified, “phosphoric acid” includes, in one or more embodiments, inorganic phosphoric acid. In the present disclosure, unless otherwise specified, “phosphonic acid” includes, in one or more embodiments, inorganic phosphonic acid.

In the present disclosure, “organic phosphonic acid” means, in one or more embodiments, 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), aminotri (methylenephosphonic acid), ethylenediaminetetra ( Methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid, ethane- 1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, α-methylphosphonosuccinic acid , And combinations thereof.

Phosphoric acids, phosphonic acids, organic phosphonic acids, and salts thereof may be used alone or in admixture of two or more. As an acid of polishing liquid composition I, in one or a plurality of embodiments, phosphoric acid or HEDP is preferable from the viewpoint of reducing long-period defects without significantly impairing the polishing rate.

When these acid salts are used, there is no particular limitation, and specific examples include metals, ammonium, alkylammonium and the like. Specific examples of the metal include metals belonging to the periodic table (long-period type) 1A, 1B, 2A, 2B, 3A, 3B, 4A, 6A, 7A, or Group 8.

The content of the acid in the polishing liquid composition I is preferably 0.001% by mass or more and 5.0% by mass or less, more preferably 0%, from the viewpoint of reducing long-period defects without significantly impairing the polishing rate. It is 0.01 mass% or more and 4.0 mass% or less, More preferably, it is 0.05 mass% or more and 3.0 mass% or less, More preferably, it is 0.1 mass% or more and 2.5 mass% or less.

Polishing liquid composition I may contain an acid different from phosphoric acids, phosphonic acid, and organic phosphonic acid in one or a plurality of embodiments as long as the effect is not impaired.

Other inorganic acids are preferred as acids different from phosphoric acids, phosphonic acids, and organic phosphonic acids. In the present disclosure, “other inorganic acids” include nitric acid, sulfuric acid, sulfurous acid, persulfuric acid, hydrochloric acid, perchloric acid, amidosulfuric acid and the like. In one or a plurality of embodiments, sulfuric acid is preferable from the viewpoint of reducing long-period defects without significantly impairing the polishing rate.

The content of the other inorganic acid in the polishing liquid composition I is preferably 0.001% by mass or more and 0.6% by mass or less from the viewpoint of reducing long-period defects without significantly impairing the polishing rate. Preferably they are 0.01 mass% or more and 0.5 mass% or less, More preferably, they are 0.05 mass% or more and 0.4 mass% or less, More preferably, they are 0.1 mass% or more and 0.3 mass% or less.

[Oxidant]
Polishing liquid composition I contains an oxidizing agent from the viewpoint of reducing long-period defects without significantly impairing the polishing rate. Examples of the oxidizing agent include peroxide, permanganic acid or a salt thereof, chromic acid or a salt thereof, peroxo acid or a salt thereof, oxygen acid or a salt thereof from the same viewpoint. Among these, hydrogen peroxide, iron (III) nitrate, peracetic acid, ammonium peroxodisulfate, iron (III) sulfate, and iron (III) ammonium sulfate are preferable, and metal ions do not adhere to the surface in terms of improving the polishing rate. From the viewpoint of being used for general purposes and inexpensive, hydrogen peroxide is more preferable. These oxidizing agents may be used alone or in admixture of two or more.

The content of the oxidizing agent in the polishing composition I is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and further preferably 0.1% by mass or more from the viewpoint of improving the polishing rate. The content is preferably 4.0% by mass or less, more preferably 2.0% by mass or less, and still more preferably 1 from the viewpoint of reducing long-period defects without significantly impairing the polishing rate. .5% by mass or less. From the viewpoint of reducing long-period defects without significantly impairing the polishing rate, the content is preferably 0.01% by mass or more and 4.0% by mass or less, more preferably 0.05% by mass or more and 2.0% by mass. % Or less, more preferably 0.1% by mass or more and 1.5% by mass or less.

[Other ingredients]
In the polishing composition I, other components can be blended as necessary. Examples of other components include thickeners, dispersants, rust inhibitors, basic substances, polishing rate improvers, surfactants, and polymer compounds. These other optional components are preferably blended in the polishing liquid composition I as long as the effects of the present disclosure are not impaired, and the total content of optional components in the polishing liquid composition I is 10% by mass or less. Preferably, 5 mass% or less is more preferable.

[water]
Polishing liquid composition I contains water as a medium. As water, distilled water, ion-exchanged water, pure water, ultrapure water, or the like can be used. The content of water in the polishing liquid composition I is preferably 61% by mass or more and 99% by mass or less, more preferably 70% by mass or more and 98% by mass or less, and still more preferably, because the handling of the polishing liquid composition becomes easy. Is 80% by mass or more and 97% by mass or less, and more preferably 85% by mass or more and 97% by mass or less.

[Alumina abrasive]
The polishing composition I preferably contains substantially no alumina abrasive grains from the viewpoint of reducing the protrusion defects. In the present disclosure, “substantially free of alumina abrasive grains” means that in one or a plurality of embodiments, it does not contain alumina particles, does not contain alumina particles in an amount that functions as abrasive grains, or polishing results. Not including an amount of alumina particles that affects the amount of alumina particles. The specific content of alumina particles in the polishing liquid composition I is not particularly limited, but is preferably 5% by mass or less, more preferably 2% by mass or less, and more preferably 1% by mass or less as a whole abrasive grain. More preferably, it is still more preferably substantially 0%.

[PH]
The pH of the polishing composition I is adjusted to 0.5 or more and 6.0 or less using the aforementioned acid or a known pH adjuster from the viewpoint of reducing long-period defects without significantly reducing the polishing rate. More preferably, 0.7 to 4.0, still more preferably 0.9 to 3.0, still more preferably 1.0 to 3.0, still more preferably 1.2 to 2. .5 or less, still more preferably 1.4 or more and 2.0 or less. The above pH is the pH of the polishing composition at 25 ° C., which can be measured using a pH meter, and is a value two minutes after immersion of the electrode in the polishing composition.

[Method for Preparing Polishing Liquid Composition I]
The polishing liquid composition I is prepared by, for example, mixing non-spherical silica particles A, spherical silica particles B, the above-described acid, the above-mentioned oxidizing agent, and water with other components as desired in a known manner. Can be prepared. In the present disclosure, the “content of the component in the polishing liquid composition” refers to the content of the component when the polishing liquid composition is used for polishing. Therefore, when the polishing liquid composition is prepared as a concentrate, the content of the components can be increased by the concentration. The mixing is not particularly limited, and can be performed using a homomixer, a homogenizer, an ultrasonic disperser, a stirrer such as a wet ball mill, or the like.

Therefore, in another aspect, the present disclosure is a method for producing a polishing liquid composition I, comprising:
(1) The ΔCV value is more than 0.0% and less than 10%, and the particle size ratio (D1 /) of the volume average particle size (D1) by the dynamic light scattering method and the specific surface area converted particle size (D2) by the BET method. (2) non-spherical silica particles A having a D2) of 2.00 to 4.00, (2) spherical silica particles B having a volume average particle diameter (D1) of 6.0 nm to 80.0 nm, and (3) Non-spherical silica containing at least one acid selected from the group consisting of phosphoric acids, phosphonic acids, organic phosphonic acids, and salts thereof, and combinations thereof, (4) an oxidizing agent, and (5) water. The mass ratio (A / B) between the particles A and the spherical silica particles B is 80/20 or more and 99/1 or less, and the total content of the nonspherical silica particles A and the spherical silica particles B with respect to the entire silica particles is 98.0. Mixing so as to exceed mass%. About. The content of each component can be as described above.

[Polished substrate]
The substrate to be polished roughly using the polishing liquid composition I is a magnetic disk substrate or a substrate used for a magnetic disk substrate. For example, a Ni—P plated aluminum alloy substrate, silicate glass, aluminosilicate glass is used. And glass substrates such as crystallized glass and tempered glass. Among these, the substrate to be polished used in the present disclosure is preferably a Ni—P plated aluminum alloy substrate from the viewpoint of strength and ease of handling. There is no restriction | limiting in particular in the shape of the said to-be-polished substrate, For example, what is necessary is just the shape which has planar parts, such as a disk shape, plate shape, slab shape, prism shape, and the shape which has curved surface parts, such as a lens. Of these, a disk-shaped substrate to be polished is suitable. In the case of a disk-shaped substrate to be polished, its outer diameter is, for example, about 2 to 95 mm, and its thickness is, for example, about 0.5 to 2 mm.

[Method of manufacturing magnetic disk substrate]
In general, a magnetic disk is obtained by polishing a glass substrate that has undergone a fine grinding process or an aluminum alloy substrate that has undergone a Ni-P plating process through a rough polishing process and a final polishing process, and forming a magnetic disk in a recording portion forming process. Manufactured. The manufacturing method of a magnetic disk substrate according to the present disclosure is a manufacturing method that includes the following steps (1) to (3) and is performed by a polishing machine different from steps (1) and (3).
(1) Rough polishing step: A step of polishing a substrate to be polished using the polishing composition I described above.
(2) Cleaning step: A step of cleaning the substrate obtained in step (1).
(3) Finish polishing: Using the step (2), the substrate obtained in the step (2) is used with a polishing liquid composition containing silica particles C (hereinafter also referred to as “polishing liquid composition II”). Polishing process.

[Step (1): Rough polishing step]
The step (1) is a step of polishing the surface to be polished of the substrate to be polished using the polishing liquid composition I in one or a plurality of embodiments, and in the other one or a plurality of embodiments, the polishing liquid composition I is supplied to the surface to be polished of the substrate to be polished, a polishing pad (hereinafter also referred to as “polishing pad A”) is brought into contact with the surface to be polished, and at least one of the polishing pad and the substrate to be polished is moved. In this step, the surface to be polished is polished. The polishing machine used in the step (1) is not particularly limited, and a known polishing machine for polishing a magnetic disk substrate can be used. Examples of the substrate to be polished in the step (1) include the above-mentioned substrates to be polished.

[Polishing pad A in step (1)]
The polishing pad A used in the step (1) of the manufacturing method according to the present disclosure is a suede type having a base layer and a foamed surface layer from the viewpoint of reducing long-period defects without significantly impairing the polishing rate. The surface layer has a compressibility of 2.5% or more.

<Structure of polishing pad A>
As the foam layer that is the surface layer of the polishing pad A, in one or a plurality of embodiments, a closed foam type and a continuous foam type can be used, but a continuous foam type is preferable from the viewpoint of discharge of polishing waste. used. Examples of the continuous foaming type polishing pad include, for example, “CMP Technology Basic Example Course Series 2nd Mechanochemical Polishing (CMP) Basics and Examples (Polishing Pad Edition) May 27, 1998 Material Global Net Corporation Edition”, Alternatively, a polishing pad as described in “CMP Science, Masahiro Kashiwa, Science Forum, Chapter 4” can be used. Here, the suede type has, in one or a plurality of embodiments, a base layer and a foam layer having spindle-shaped pores perpendicular to the base layer as described in JP-A No. 11-335979. Refers to the structure.

The suede type polishing pad is manufactured by the following method in one or a plurality of embodiments. A solution in which polyurethane elastomer is dissolved in a solvent such as dimethylformamide (DMF) is applied on a base layer made of polyethylene terephthalate (PET), and then immersed in water or a mixed solution of water and a solvent for polyurethane elastomer solution. Then, wet coagulation is carried out, followed by washing with water for solvent removal and drying. As a result, a foam layer having spindle-shaped pores perpendicular to the base layer is formed on the base layer. And by polishing the surface of the obtained foam layer with sandpaper or the like, a suede type polishing pad having a foam layer having a pore portion on the surface and a spindle-shaped pore perpendicular to the base layer Is obtained.

<Material of polishing pad A>
Examples of the material of the base layer of the polishing pad A include, in one or a plurality of embodiments, a non-woven fabric made of natural fibers such as cotton or a synthetic fiber, a base layer obtained by filling a rubber-like substance such as styrene butadiene rubber, and the like. However, a polyethylene terephthalate (PET) film and a polyester film are preferable, and a PET film is more preferable from the viewpoint of reducing microwaviness and obtaining a resin film having high hardness. Examples of the material of the foam layer (surface layer) of the polishing pad A include polyurethane elastomer, polystyrene, polyester, polyvinyl chloride, natural rubber, and synthetic rubber in one or a plurality of embodiments. From the viewpoint of reducing long-period defects without loss, polyurethane elastomers are preferred. In this specification, “undulation” of a substrate refers to irregularities on the surface of the substrate having a wavelength longer than the roughness.

<Compression rate of polishing pad A>
The compression rate of the foam layer (surface layer) of the polishing pad A is 2.5% or more, preferably 20.0% or less, from the viewpoint of reducing long-period defects without significantly impairing the polishing rate. Preferably it is 15.0% or less, More preferably, it is 10.0% or less, More preferably, it is 7.0% or less, More preferably, it is 5.0% or less.

The compressibility of the polishing pad can be measured by a compression tester based on the compressibility measurement method described in Japanese Industrial Standard (JIS) L1096. That is, the value obtained by subtracting the thickness (T1) of the polishing pad measured under 1000 g / cm ² from the thickness (T0) of the polishing pad measured under standard pressure (100 g / cm ² ) is divided by T0. It can be determined by multiplying the value by 100. The compressibility of the polishing pad can be controlled by, for example, the thickness of the foam layer, the pore size on the base layer side of the foam layer, or the material of the base layer.

<Average pore diameter of polishing pad A>
The average pore diameter of the pores on the surface of the polishing pad A is preferably 10 μm or more and 100 μm or less, more preferably 15 μm or more and 80 μm or less, and still more preferably 20 μm, from the viewpoint of reducing long-period defects without significantly impairing the polishing rate. The thickness is 60 μm or less, and more preferably 25 μm or more and 55 μm or less.

The average pore size of the pores on the surface of the polishing pad is such that pigments such as carbon black, a hydrophilic activator that promotes foaming, or a hydrophobic activator that stabilizes wet coagulation of the polyurethane elastomer with respect to the polyurethane elastomer raw material. It can control by adding an additive. And the said average pore diameter can be calculated | required with the following method. First, the surface of the polishing pad is observed with a scanning electron microscope (preferably 100 to 300 times), and an image is taken into a personal computer (PC). Then, the captured image is analyzed by image analysis software on a PC, and the average pore diameter can be obtained as the average diameter of the equivalent circle diameter of the pores. For example, WinROOF (Mitani Corporation) can be used as the image analysis software.

<Thickness of polishing pad A>
The thickness of the polishing pad A is preferably from 0.7 mm to 1.5 mm, more preferably from 0.8 mm to 1.4 mm, and still more preferably from the viewpoint of reducing long-period defects without significantly impairing the polishing rate. It is 0.8 mm or more and 1.3 mm or less, and more preferably 0.9 mm or more and 1.3 mm or less.

[Polishing load in step (1)]
In the present disclosure, the polishing load means the pressure of the surface plate applied to the polishing surface of the substrate to be polished during polishing. The polishing load in the step (1) is preferably 30 kPa or less, more preferably 25 kPa or less, still more preferably 20 kPa or less, still more preferably 18 kPa or less, from the viewpoint of reducing long-period defects without significantly impairing the polishing rate. Even more preferably, it is 16 kPa or less, and still more preferably 14 kPa or less. The polishing load is preferably 3 kPa or more, more preferably 5 kPa or more, still more preferably 7 kPa or more, even more preferably 8 kPa or more, and even more preferably from the viewpoint of reducing long-period defects without significantly impairing the polishing rate. 9 kPa or more. The polishing load is preferably 3 kPa or more and 30 kPa or less, more preferably 5 kPa or more and 25 kPa or less, still more preferably 7 kPa or more and 20 kPa or less, and even more preferably 8 kPa, from the viewpoint of reducing long-period defects without significantly impairing the polishing rate. 18 kPa or less, still more preferably 9 kPa or more and 16 kPa or less, and even more preferably 9 kPa or more and 14 kPa or less. The polishing load can be adjusted by applying air pressure or weight to the surface plate or the substrate.

[Polishing amount in step (1)]
In the step (1), the polishing amount per substrate to be polished (diameter 95 mm) is 110 mg or more and 160 mg or less from the viewpoint of reducing long-period defects without significantly reducing the polishing rate in one or a plurality of embodiments. More preferably, it is 115 mg or more and 155 mg or less, More preferably, it is 120 mg or more and 150 mg or less. For the substrates to be polished having different diameters, the above range is applied according to the area. The polishing in the step (1) in the production method according to the present disclosure uses the polishing composition I containing the above-mentioned predetermined non-spherical silica particles A, spherical silica particles B, acid, oxidizing agent, and water. Long period defects can be effectively removed with a polishing amount in the range.

[Supply speed of polishing liquid composition I in step (1)]
The supply rate of the polishing liquid composition I in the step (1) is preferably 2.5 mL / min or less per 1 cm ^{2 of the} substrate to be polished, more preferably 2.0 mL / min or less, and still more preferably 1 from the economical viewpoint. 0.5 mL / min or less, still more preferably 1.0 mL / min or less, even more preferably 0.5 mL / min or less, and even more preferably 0.2 mL / min or less. From the viewpoint of improving the polishing rate, the supply rate is preferably 0.01 mL / min or more per 1 cm ^{2 of the} substrate to be polished, more preferably 0.03 mL / min or more, and further preferably 0.05 mL / min or more. The supply rate is preferably 0.01 mL / min or more and 2.5 mL / min or less, more preferably 0.03 mL / min or more, per 1 cm ^{2 of the} substrate to be polished, from the viewpoint of economy and improvement of the polishing rate. 0 mL / min or less, more preferably 0.03 mL / min or more and 1.5 mL / min or less, still more preferably 0.03 mL / min or more and 1.0 mL / min or less, still more preferably 0.05 mL / min or more and 0. 5 mL / min or less, still more preferably 0.05 mL / min or more and 0.2 mL / min or less.

[Supply amount of polishing composition I in step (1)]
The supply amount of the polishing liquid composition I in the step (1) depends on the supply speed of the polishing liquid composition I, but is preferably further reduced from the viewpoint of economy. In one or a plurality of embodiments of the present disclosure, it is conceivable that the polishing liquid composition I can act on the substrate more efficiently, so that the supply amount of the polishing liquid can be reduced from the conventional supply amount. The reduction efficiency of the polishing liquid supply amount in the present disclosure can be specifically evaluated by the method described in the examples.

[Method for supplying polishing liquid composition I in step (1) to polishing machine]
As a method of supplying the polishing composition I to the polishing machine, for example, a method of continuously supplying using a pump or the like can be mentioned. When supplying the polishing liquid composition I to the polishing machine, in addition to the method of supplying it as a single liquid containing all the components, considering the storage stability of the polishing liquid composition I, a plurality of component liquids for blending It can also be divided into two liquids or more. In the latter case, for example, the plurality of compounding component liquids are mixed into the polishing liquid composition I in the supply pipe or on the substrate to be polished.

[Step (2): Cleaning step]
Step (2) is a step of cleaning the substrate obtained in step (1). Step (2) is a step of cleaning the substrate that has been subjected to the rough polishing in step (1) with a cleaning composition in one or more embodiments. Although the cleaning method in the step (2) is not particularly limited, in one or a plurality of embodiments, the method of immersing the substrate obtained in the step (1) in the cleaning composition (cleaning method a), and the cleaning agent The method (cleaning method b) which injects a composition and supplies a cleaning composition on the surface of the board | substrate obtained by process (1) is mentioned.

<Washing method a>
In the cleaning method a, the conditions for immersing the substrate in the cleaning composition are not particularly limited. For example, the temperature of the cleaning composition is 20 to 100 ° C. from the viewpoint of safety and operability. The immersion time is preferably from 10 seconds to 30 minutes from the viewpoint of the cleaning properties and production efficiency of the cleaning composition. From the viewpoint of enhancing the removability of the residue and the dispersibility of the residue (cleanability for the residue), it is preferable that ultrasonic vibration is applied to the cleaning composition. The frequency of the ultrasonic wave is preferably 20 kHz to 2000 kHz, more preferably 40 kHz to 2000 kHz, and still more preferably 40 kHz to 1500 kHz.

<Washing method b>
In the cleaning method b, from the viewpoint of promoting the cleaning property with respect to the residue and the solubility of the oil, the cleaning agent composition to which ultrasonic vibration is applied is injected to bring the cleaning agent composition into contact with the surface of the substrate. Or cleaning the surface by supplying the cleaning composition onto the surface of the substrate to be cleaned by injection and rubbing the surface supplied with the cleaning composition with a cleaning brush. preferable. Further, in the cleaning method b, the cleaning composition to which ultrasonic vibration is applied is supplied to the surface to be cleaned by injection, and the surface to which the cleaning composition is supplied is applied with a cleaning brush. It is preferable to perform washing.

As means for supplying the cleaning composition onto the surface of the substrate to be cleaned, known means such as a spray nozzle can be used. There is no restriction | limiting in particular as a brush for washing | cleaning, For example, well-known things, such as a nylon brush and a PVA (polyvinyl alcohol) sponge brush, can be used. The ultrasonic frequency may be the same as the value preferably employed in the cleaning method a.

In the step (2), in addition to the cleaning method a and / or the cleaning method b, one or more steps using known cleaning such as rocking cleaning, cleaning using rotation of a spinner, paddle cleaning, scrub cleaning, and the like are included. But you can.

[Cleaning composition in step (2)]
As a cleaning composition of a process (2), in one or some embodiment, what contains an alkali agent, water, and various additives as needed can be used.

<Alkaline agent in cleaning composition>
The alkaline agent used in the cleaning composition may be either an inorganic alkaline agent or an organic alkaline agent. Examples of the inorganic alkaline agent include ammonia, potassium hydroxide, and sodium hydroxide. Examples of the organic alkali agent include one or more selected from the group consisting of hydroxyalkylamine, tetramethylammonium hydroxide, and choline. These alkaline agents may be used alone or in combination of two or more. From the viewpoint of improving the detergency of the residue on the substrate of the cleaning composition and improving the storage stability, the alkaline agent includes potassium hydroxide, sodium hydroxide, monoethanolamine, methyldiethanolamine, and aminoethyl. At least one selected from the group consisting of ethanolamine is preferable, and at least one selected from the group consisting of potassium hydroxide and sodium hydroxide is more preferable.

The content of the alkaline agent in the cleaning composition is 0.05 from the viewpoint of improving the cleaning properties of the cleaning composition on the residue on the substrate and increasing the safety when handling the cleaning composition. The content is preferably from 10% by mass to 10% by mass, more preferably from 0.08% by mass to 5% by mass, and still more preferably from 0.1% by mass to 3% by mass.

The pH of the cleaning composition is preferably 8 or more and 14 or less, more preferably 9 or more and 13 or less, still more preferably 10 or more and 13 or less, and even more, from the viewpoint of improving the detergency with respect to the residue on the substrate. Preferably they are 11 or more and 13 or less. In addition, said pH is pH of the cleaning composition at 25 degreeC, can be measured using a pH meter, and is a numerical value 2 minutes after immersion in the cleaning composition of an electrode.

<Various additives in cleaning composition>
In addition to alkaline agents, the detergent composition includes nonionic surfactants, chelating agents, ether carboxylates or fatty acids, anionic surfactants, water-soluble polymers, antifoaming agents (surfactants corresponding to ingredients are Except alcohol), preservatives, antioxidants, and the like.

The content of components other than water in the cleaning composition is from the viewpoint of coexistence of a concentration sufficient to improve workability, economy and storage stability, and improvement in storage stability. When the total content of water and components other than water is 100% by mass, it is preferably 10% by mass to 60% by mass, more preferably 15% by mass to 50% by mass, Preferably they are 15 to 40 mass%.

The cleaning composition is used after diluting. In consideration of cleaning efficiency, the dilution rate is preferably 10 to 500 times, more preferably 20 to 200 times, and still more preferably 50 to 100 times. The water for dilution may be the same as that of the polishing composition I described above. The cleaning composition can be a concentrate based on the dilution ratio. Therefore, in the case of a concentrate, the content of components other than water in the cleaning composition is preferably 0.02 when the total of the content of water and the content of components other than water is 100% by mass. It is not less than 6% by mass and not more than 6% by mass, more preferably not less than 0.1% by mass and not more than 3% by mass, and further preferably not less than 0.15% by mass and not more than 1% by mass.

[Step (3): Final polishing step]
A process (3) is a process of grind | polishing the grinding | polishing target surface of the board | substrate obtained at the process (2) using the polishing liquid composition II containing the silica particle C in one or some embodiment. In one or a plurality of other embodiments, the step (3) supplies the polishing liquid composition II containing the silica particles C to the surface to be polished of the substrate obtained in the step (2). In this step, a polishing pad is brought into contact and at least one of the polishing pad and the substrate to be polished is moved to polish the surface to be polished. The polishing machine used in step (3) is used in step (1) from the viewpoint of reducing protrusion defects and using pads having different pore diameters from rough polishing in order to efficiently reduce other surface defects. This polishing machine is different from the polishing machine used.

The manufacturing method according to the present disclosure includes a rough polishing step in step (1), a cleaning step in step (2), and a final polishing step in step (3), thereby greatly impairing the polishing rate of rough polishing. Therefore, it is possible to efficiently manufacture a substrate in which long-period defects are reduced and protrusion defects after finish polishing are reduced.

[Polishing liquid composition II in step (3)]
Polishing liquid composition II used at a process (3) contains the silica particle C as an abrasive from a viewpoint of the projection defect reduction after final polishing. The silica particles C used are preferably colloidal silica from the viewpoint of reducing long wavelength waviness after finish polishing. The polishing composition II preferably does not substantially contain alumina abrasive grains from the viewpoint of reducing protrusion defects after finish polishing. The silica particles C are spherical in one or more embodiments. In this specification, “long wavelength undulation” refers to undulation observed with a wavelength of 500 to 5000 μm. By reducing the waviness of the substrate surface after polishing, the flying height of the magnetic head can be reduced, and the recording density of the magnetic disk substrate can be improved.

The volume average particle diameter (D1) by the dynamic light scattering method of the silica particles C used in the polishing composition II is preferably 5 nm or more and 50 nm or less, more preferably 10 nm, from the viewpoint of reducing protrusion defects after finish polishing. It is not less than 45 nm, more preferably not less than 15 nm and not more than 40 nm, and still more preferably not less than 20 nm and not more than 35 nm. The volume average particle diameter (D1) of the silica particles C by the dynamic light scattering method is the volume average particle diameter (D1) of the nonspherical silica particles A by the dynamic light scattering method from the viewpoint of reducing the protrusion defects after finish polishing. Preferably it is smaller.

In one or a plurality of embodiments, the CV90 of the silica particles C is preferably 10.0% or more, more preferably 15.0% or more, from the viewpoint of suppressing a decrease in polishing rate and reducing protrusion defects after finish polishing. More preferably, it is 20.0% or more, and from the same viewpoint, it is preferably 35.0% or less, more preferably 32.0% or less, still more preferably 30.0% or less. In one or a plurality of embodiments, the CV90 of the spherical silica particles B is 10.0% or more and 35.0% or less, preferably 15.0% or more and 32.0% or less, more preferably, from the same viewpoint. Is 20.0% or more and 30.0% or less.

The content of the silica particles C in the polishing liquid composition II is preferably 0.5% by mass or more and 20% by mass or less, and preferably 1.0% by mass or more from the viewpoint of reducing long-wave waviness and protrusion defects after finish polishing. 15 mass% or less is more preferable, 3.0 mass% or more and 13 mass% or less are still more preferable, and 4.0 mass% or more and 10 mass% or less are still more preferable.

Polishing liquid composition II contains 1 or more types chosen from the polymer which has a heterocyclic aromatic compound, a polyvalent amine compound, and an anionic group from a viewpoint of reducing the long wavelength waviness and protrusion defect after final polishing. It is preferable to include two or more types, and it is more preferable to include a heterocyclic aromatic compound, a polyvalent amine compound, and a polymer having an anionic group.

Polishing liquid composition II preferably contains an acid and an oxidizing agent from the viewpoint of improving the polishing rate. About the preferable usage aspect of an acid and an oxidizing agent, it is the same as that of the case of the above-mentioned polishing liquid composition I. The water used for the polishing liquid composition II, the pH of the polishing liquid composition II, and the method for preparing the polishing liquid composition II are the same as those for the polishing liquid composition I described above.

[Polishing pad in step (3)]
As the polishing pad used in the step (3), the same type of polishing pad as that used in the step (1) can be used. The average pore diameter of the polishing pad used in the step (3) is preferably 1 μm or more and 50 μm or less, more preferably 2 μm or more and 40 μm or less, and still more preferably, from the viewpoint of reducing long wavelength waviness and protrusion defects after finish polishing. 3 μm or more and 30 μm or less.

[Polishing load of step (3)]
The polishing load in the step (3) is preferably 16 kPa or less, more preferably 14 kPa or less, and still more preferably 13 kPa or less, from the viewpoint of reducing long wavelength waviness and protrusion defects after finish polishing. The polishing load is preferably 7.5 kPa or more, more preferably 8.5 kPa or more, and further preferably 9.5 kPa or more, from the viewpoint of reducing long wavelength waviness and protrusion defects after finish polishing. The polishing load is preferably 7.5 kPa or more and 16 kPa or less, more preferably 8.5 kPa or more and 14 kPa or less, and further preferably 9.5 kPa or more and 13 kPa or less, from the viewpoint of reducing long wavelength waviness and protrusion defects after finish polishing. is there.

[Polishing amount in step (3)]
In the step (3), the polishing amount per unit area (1 cm ² ) of the substrate to be polished and the polishing time per minute is preferably 0.02 mg or more from the viewpoint of reducing long wavelength waviness and protrusion defects after finish polishing. More preferably, it is 0.03 mg or more, More preferably, it is 0.04 mg or more. The polishing amount is preferably 0.15 mg or less, more preferably 0.12 mg or less, and still more preferably 0.10 mg or less from the viewpoint of improving productivity. Therefore, the polishing amount is preferably 0.02 mg or more and 0.15 mg or less, more preferably 0.03 mg or more and 0.12 mg or less, and further preferably 0.04 mg or more and 0.10 mg or less from the same viewpoint as described above. .

In the step (3), the supply rate of the polishing liquid composition II and the method of supplying the polishing liquid composition II to the polishing machine are the same as in the case of the polishing liquid composition I described above.

According to the manufacturing method of the present disclosure, in one or a plurality of embodiments, since long-period defects can be reduced without significantly impairing the polishing rate in rough polishing, a magnetic disk substrate with reduced protrusion defects can be obtained with a high substrate yield. Thus, the effect of being able to manufacture with high productivity can be achieved.

[Polishing method]
As another aspect, the present disclosure relates to a polishing method having the above-described step (1), step (2), and step (3). Polishing substrate, polishing liquid composition I, non-spherical silica particles A, spherical silica particles B, polishing liquid composition II, silica particles C, polishing method and conditions in steps (1) to (3), cleaning composition, The cleaning method can be the same as the method for manufacturing the magnetic disk substrate according to the present disclosure described above.

By using the polishing method of the present disclosure, in one or a plurality of embodiments, it is possible to reduce long-period defects without significantly reducing the polishing rate in rough polishing, so that a magnetic disk substrate with reduced protrusion defects is a high substrate. The effect that it can manufacture with sufficient productivity with a yield can be show | played.

In one or a plurality of embodiments, a manufacturing method and a polishing method according to the present disclosure include a first polishing machine 51 that polishes (roughly polishes) a substrate to be polished using a polishing composition I as shown in FIG. A magnetic disk substrate polishing system comprising: a cleaning unit 52 for cleaning the substrate polished by the first polishing machine 51; and a second polishing machine 53 for polishing the cleaned substrate using the polishing composition II. Can be performed. Therefore, in one aspect, the present disclosure provides a first polishing machine that performs the polishing in the step (1), a cleaning unit that performs the cleaning in the step (2), and a second that performs the polishing in the step (3). The present invention relates to a polishing system for a magnetic disk substrate provided with a polishing machine. The polishing liquid composition I and the polishing liquid composition II are as described above. The substrate to be polished, the polishing pad used in each polishing machine, the polishing method and conditions, the cleaning composition, and the cleaning method are as described above. It can be the same as the manufacturing method of the magnetic disk substrate according to the present disclosure.

In one or more embodiments of the polishing system according to the present disclosure, the polishing amount for at least one substrate to be polished (diameter: 95 mm) polished by the first polishing machine 51 is preferably 110 mg or more and 160 mg or less. It may have a means (polishing control unit) (not shown) for confirming that it is preferably 115 mg or more and 155 mg or less, more preferably 120 mg or more and 150 mg or less. In one or a plurality of embodiments, the means (polishing control unit) controls the first polishing machine 51 based on the polishing amount of the substrate. Here, an embodiment of the operation of the polishing system according to the present disclosure (polishing step of the method for manufacturing a magnetic disk substrate) will be described with reference to FIG. 5 and FIG. First, the substrate to be polished is polished (roughly polished) by the first polishing machine 51 (step S61). Then, the polishing controller determines whether the polishing amount of the substrate by the first polishing machine 51 is within a predetermined polishing amount range (110 to 160 mg in this case) (step S62). When the polishing amount is within the predetermined polishing amount, the substrate after rough polishing is cleaned by the cleaning unit 52 (step S62), and the cleaned substrate is polished by the second polishing machine 53 (step S63). On the other hand, when the polishing amount is not within the predetermined polishing amount, the polishing is continued or stopped in the first polishing machine 51 (step S65).

The present disclosure further relates to one or more embodiments below.

<1> (1) A step of polishing the surface to be polished of the substrate to be polished using the polishing composition I, (2) a step of cleaning the substrate obtained in step (1), and (3) step ( A magnetic disk substrate having a step of polishing the substrate obtained in 2) using a polishing composition II containing silica particles C, and performing the steps (1) and (3) with another polishing machine. It is a manufacturing method, Comprising: (i) The said polishing liquid composition I of the said process (1) contains the nonspherical silica particle A, the spherical silica particle B, an acid, an oxidizing agent, and water, (ii) The said process ( In the polishing composition I of 1), the mass ratio (A / B) of the non-spherical silica particles A and the spherical silica particles B is 80/20 or more and 99/1 or less, and the non-spherical silica with respect to the entire silica particles The total content of the particles A and the spherical silica particles B exceeds 98.0% by mass, (iii) The ΔCV value of the non-spherical silica particle A is more than 0.0% and less than 10%, where the ΔCV value is a standard deviation based on a scattering intensity distribution at a detection angle of 30 ° by the dynamic light scattering method. Divide by the average particle size based on the intensity distribution and multiply by 100 (CV30) and the standard deviation based on the scattering intensity distribution at a detection angle of 90 ° divided by the average particle size based on the scattering intensity distribution and multiply by 100 (Iv) The volume average particle diameter (D1) of the non-spherical silica particles A by dynamic light scattering method and the specific surface area conversion by BET method (ΔCV = CV30−CV90) The particle size ratio (D1 / D2) of the particle size (D2) is 2.00 or more and 4.00 or less, and (v) the spherical silica particle B has a volume average particle size (D1) by a dynamic light scattering method. 6.0 nm or more and 80.0 nm or less, i) said acid, phosphoric acids, phosphonic acids, organic phosphonic acids, and is selected from the group consisting of method of manufacturing a magnetic disk substrate.

<2> The non-spherical silica particles A are at least one selected from the group consisting of confetti-type silica particles A1, deformed-type silica particles A2, deformed and confetti-type silica particles A3, and combinations thereof. <1> The manufacturing method of description.
<3> The ΔCV value of the non-spherical silica particles A is preferably more than 0.0%, more preferably 0.2% or more, still more preferably 0.3% or more, and even more preferably 0.4% or more. The production method according to <1> or <2>.
<4> The non-spherical silica particles A preferably have a ΔCV value of less than 10.0%, more preferably 8.0% or less, still more preferably 7.0% or less, and even more preferably 4.0. % Or less, The manufacturing method in any one of <1> to <3>.
<5> The ΔCV value of the non-spherical silica particles A is preferably more than 0.0% and less than 10.0%, more preferably 0.2% or more and 8.0% or less, and more preferably 0. The manufacturing method according to any one of <1> to <4>, which is 0.3% or more and 7.0% or less, and more preferably 0.4% or more and 4.0% or less.
<6> The volume average particle diameter (D1) of the non-spherical silica particles A is preferably 120.0 nm or more, more preferably 150.0 nm or more, still more preferably 160.0 nm or more, and even more preferably 170.0 nm or more. The production method according to any one of <1> to <5>, which is still more preferably 180.0 nm or more, still more preferably 190.0 nm or more, and even more preferably 200.0 nm or more.
<7> The volume average particle diameter (D1) of the non-spherical silica particles A is preferably less than 300.0 nm, more preferably less than 260.0 nm, still more preferably less than 250.0 nm, and even more preferably less than 220.0 nm. Even more preferably, the production method according to any one of <1> to <6>, which is less than 210.0 nm.
<8> The volume average particle diameter (D1) of the non-spherical silica particles A is preferably 120.0 nm or more and less than 300.0 nm, more preferably 120.0 nm or more and less than 260.0 nm, and further preferably 150.0 nm or more and 260. Less than 0.0 nm, even more preferably from 160.0 nm to less than 260.0 nm, even more preferably from 170.0 nm to less than 260.0 nm, even more preferably from 180.0 nm to less than 250.0 nm, even more preferably 190.0 nm The production method according to any one of <1> to <7>, which is at least 220.0 nm and more preferably at least 200.0 nm and less than 210.0 nm.
<9> A volume ratio (D1 / D2) of the volume average particle diameter (D1) of the non-spherical silica particles A by a dynamic light scattering method and a specific surface area conversion particle diameter (D2) by a BET method is preferably 2. The production method according to any one of <1> to <8>, which is 00 or more, more preferably 2.50 or more, still more preferably 3.00 or more, and even more preferably 3.50 or more.
<10> The particle diameter ratio (D1 / D2) of the volume average particle diameter (D1) of the non-spherical silica particles A by the dynamic light scattering method and the specific surface area equivalent particle diameter (D2) by the BET method is preferably 4. The production method according to any one of <1> to <9>, which is 00 or less, more preferably 3.90 or less, and still more preferably 3.80 or less.
<11> The particle diameter ratio (D1 / D2) of the volume average particle diameter (D1) of the non-spherical silica particles A by the dynamic light scattering method and the specific surface area converted particle diameter (D2) by the BET method is preferably 2. 00 or more and 4.00 or less, more preferably 2.50 or more and 3.90 or less, still more preferably 3.00 or more and 3.90 or less, and even more preferably 3.50 or more and 3.80 or less, from <1> The manufacturing method in any one of <10>.
<12> The CV90 of the non-spherical silica particles A is preferably 20.0% or more, more preferably 25.0% or more, and further preferably 27.0% or more, any one of <1> to <11> The manufacturing method of crab.
<13> The CV90 of the non-spherical silica particles A is preferably 40.0% or less, more preferably 38.0% or less, still more preferably 35.0% or less, and even more preferably 32.0% or less. <1> to the production method according to any one of <12>.
<14> The CV90 of the non-spherical silica particles A is preferably 20.0% or more and 40.0% or less, more preferably 25.0% or more and 38.0% or less, and further preferably 25.0 or more and 35.0%. % Or less, and even more preferably 27.0% or more and 32.0% or less, according to any one of <1> to <13>.
<15> The content of the non-spherical silica particles A in the polishing composition I is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1% by mass or more, and even more. The production method according to any one of <1> to <14>, preferably 2% by mass or more.
<16> The content of the non-spherical silica particles A in the polishing composition I is preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less, and even more preferably 15% by mass. % Or less, The manufacturing method in any one of <1> to <15>.
<17> The content of the non-spherical silica particles A in the polishing composition I is preferably 0.1% by mass to 30% by mass, more preferably 0.5% by mass to 25% by mass, and still more preferably. Is 1% by mass or more and 20% by mass or less, and more preferably 2% by mass or more and 15% by mass or less. The production method according to any one of <1> to <16>.
<18> The production method according to any one of <1> to <17>, wherein the non-spherical silica particles A are silica particles produced by a particle growth method using water glass as a raw material.
<19> The ΔCV value of the spherical silica particles B is preferably more than 0.0%, more preferably 0.2% or more, still more preferably 0.3% or more, and even more preferably 0.4% or more. The production method according to any one of <1> to <18>.
<20> The ΔCV value of the spherical silica particles B is preferably less than 10.0%, more preferably 8.0% or less, still more preferably 7.0% or less, and even more preferably 4.0%. The production method according to any one of <1> to <19>, which is as follows.
<21> The ΔCV value of the spherical silica particles B is preferably more than 0.0% and less than 10.0%, more preferably 0.2% or more and 8.0% or less, and still more preferably 0.8. The production method according to any one of <1> to <20>, which is 3% or more and 7.0% or less, and more preferably 0.4% or more and 4.0% or less.
<22> The method according to any one of <1> to <21>, wherein the spherical silica particles B have a volume average particle diameter (D1) of preferably 6.0 nm or more, more preferably 7.0 nm or more. .
<23> The volume average particle diameter (D1) of the spherical silica particles B is preferably 80.0 nm or less, more preferably 70.0 nm or less, and more preferably 60.0 nm or less. <1> to <22> The manufacturing method in any one of.
<24> The volume average particle diameter (D1) of the spherical silica particles B is preferably 6.0 nm or more and 80.0 nm or less, more preferably 6.0 nm or more and 70.0 nm or less, and still more preferably 7.0 nm or more and 60.60. The production method according to any one of <1> to <23>, which is 0 nm or less.
<25> The spherical silica particles B are two types of particles having different particle diameters, and the two types of particles are a spherical particle of 6.0 nm to 15.0 nm and a spherical particle of 15.5 nm to 70.0 nm. Or a combination of spherical particles of 15.5 nm or more and 30.0 nm or less and spherical particles of 30.5 nm or more and 70.0 nm or less, according to any one of <1> to <24> .
<26> The particle size ratio (D1 / D2) of the volume average particle diameter (D1) by the dynamic light scattering method of the spherical silica particles B and the specific surface area converted particle diameter (D2) by the BET method is preferably 1.00. The production method according to any one of <1> to <25>, more preferably 1.10 or more, and still more preferably 1.15 or more.
<27> The volume ratio (D1 / D2) of the volume average particle diameter (D1) by the dynamic light scattering method of the spherical silica particles B and the specific surface area converted particle diameter (D2) by the BET method is preferably 1.50. Hereinafter, the production method according to any one of <1> to <26>, more preferably 1.40 or less, and still more preferably 1.30 or less.
<28> The particle diameter ratio (D1 / D2) of the volume average particle diameter (D1) by the dynamic light scattering method of the spherical silica particles B and the specific surface area converted particle diameter (D2) by the BET method is preferably 1.00. The production method according to any one of <1> to <27>, which is 1.50 or more, preferably 1.10 or more and 1.40 or less, more preferably 1.15 or more and 1.30 or less.
<29> Any of <1> to <28>, wherein CV90 of the spherical silica particles B is preferably 10.0% or more, more preferably 15.0% or more, and further preferably 20.0% or more. The manufacturing method as described in.
<30> Any of <1> to <29>, wherein CV90 of the spherical silica particles B is preferably 35.0% or less, more preferably 32.0% or less, and even more preferably 30.0% or less. The manufacturing method as described in.
<31> The CV90 of the spherical silica particles B is preferably 10.0% or more and 35.0% or less, more preferably 15.0% or more and 32.0% or less, and further preferably 20.0% or more. The production method according to any one of <1> to <30>, which is 30.0% or less.
<32> The content of the spherical silica particles B in the polishing composition I is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more. More preferably, it is 0.2 mass% or more, The manufacturing method in any one of <1> to <31>.
<33> The content of the spherical silica particles B in the polishing composition I is preferably 3% by mass or less, more preferably 2.5% by mass or less, still more preferably 2% by mass or less, and still more preferably 1%. The manufacturing method in any one of <1> to <32> which is 0.5 mass% or less.
<34> The total overlap frequency of the volume particle size distribution of the non-spherical silica particles A and the spherical silica particles B in the polishing liquid composition I is preferably 0% to 50%, more preferably 10% to 45%. The production method according to any one of <1> to <33>, more preferably 15% to 40%, and still more preferably 20% to 35%.
<35> The mass ratio (A / B) of the content of the non-spherical silica particles A and the spherical silica particles B in the polishing composition I is preferably 80/20 or more, more preferably 85/15 or more, The production method according to any one of <1> to <34>, which is preferably 90/10 or more.
<36> The mass ratio (A / B) of the content of non-spherical silica particles A and spherical silica particles B in the polishing composition I is preferably 99/1 or less, more preferably 95/5 or less, and further The production method according to any one of <1> to <35>, which is preferably 92/8 or less.
<37> The total content of the non-spherical silica particles A and the spherical silica particles B with respect to the entire silica particles in the polishing composition I is preferably more than 98.0% by mass, more preferably 98.5% by mass or more. More preferably 99.0% by weight or more, even more preferably 99.5% by weight or more, even more preferably 99.8% by weight or more, even more preferably substantially 100% by weight, <1 > To <36>.
<38> The content of the acid in the polishing liquid composition I is preferably 0.001% by mass to 5% by mass, more preferably 0.01% by mass to 4% by mass, and still more preferably 0.8%. The production method according to any one of <1> to <37>, which is from 05% by mass to 3% by mass, and more preferably from 0.1% by mass to 2.5% by mass.
<39> The production method according to any one of <1> to <38>, wherein the polishing liquid composition I does not substantially contain alumina particles.
<40> The pH of the polishing composition I is preferably 0.5 or more and 6.0 or less, more preferably 0.7 or more and 4.0 or less, still more preferably 0.9 or more and 3.0 or less, and even more. It is preferably 1.0 or more and 3.0 or less, more preferably 1.2 or more and 2.5 or less, and even more preferably 1.4 or more and 2.0 or less, and any one of <1> to <39> The manufacturing method as described.
<41> The method according to any one of <1> to <40>, wherein the polishing object of the polishing liquid composition I is a Ni—P plated aluminum alloy substrate.
<42> The polishing amount per substrate to be polished (diameter 95 mm) in the step (1) is preferably 110 mg or more and 160 mg or less, more preferably 115 mg or more and 155 mg or less, and further preferably 120 mg or more and 150 mg or less. 1> to <41>.
<43> A method for polishing a magnetic disk substrate, comprising the steps (1) to (3) in the method for producing a magnetic disk substrate according to any one of <1> to <42>.
<44> A first polishing machine that performs the polishing in the step (1) in the method of manufacturing a magnetic disk substrate according to any one of <1> to <42>, and any one of <1> to <42> A cleaning unit for performing the cleaning in the step (2) in the method for manufacturing a magnetic disk substrate, and a second for performing the polishing in the step (3) in the method for manufacturing the magnetic disk substrate according to any one of <1> to <42>. Magnetic disk substrate polishing system comprising a polishing machine.

Hereinafter, the present disclosure will be described in more detail by way of examples. However, these examples are illustrative, and the present disclosure is not limited to these examples.

A polishing liquid composition I used in step (1) and a polishing liquid composition II used in step (3) were prepared as described below, and polishing of the substrate to be polished under the following conditions including steps (1) to (3) Went. The preparation method of the polishing liquid composition, the additive used, the measurement method of each parameter, the polishing conditions (polishing method) and the evaluation method are as follows.

1. Preparation of polishing liquid composition [Preparation of polishing liquid composition I used in step (1) (rough polishing)]
Using the non-spherical silica abrasive grains A and spherical silica particles B (both colloidal silica particles) shown in Table 1, the acid, hydrogen peroxide, and water shown in Table 2, a polishing liquid composition I used in the step (1) was prepared. (Examples 1 to 16, Reference Examples 1 to 9, Comparative Examples 1 to 6) (Table 2). The content of each component in the polishing composition I was colloidal silica particles: 6.0% by mass, acid: 1.0-2.4% by mass, and hydrogen peroxide: 1.0% by mass. The pH of the polishing composition I was 1.2-1.9. The colloidal silica particles of the silica abrasive grains in Table 1 are produced by the water glass method. The pH was measured using a pH meter (manufactured by TOA DK Corporation). The numerical value after 2 minutes of immersing the electrode in the polishing composition was adopted (hereinafter the same).

The type of the non-spherical silica abrasive grain A in Table 1 is a classification that can be discriminated by an observation photograph of a transmission electron microscope (TEM) and analysis using the same in one or a plurality of embodiments.
“Atypical silica particles” refers to non-spherical silica particles having a shape in which two or more particles are aggregated or fused. In one or a plurality of embodiments, the irregular-shaped silica particles refer to particles having a shape in which two or more particles having a particle size of 1.5 times or less are aggregated or fused.
“Konpeira type silica particles” refers to non-spherical silica particles having unique ridges on the surface of the spherical particles. In one or a plurality of embodiments, the confetti type silica particles refer to particles having a shape in which two or more particles different in particle size by 5 times or more are aggregated or fused.
An example of an electron microscope (TEM) observation photograph of an irregular-shaped colloidal silica abrasive grain is shown in FIG. 1, and an example of an electron microscope (TEM) observation photograph of a confetti-type colloidal silica abrasive grain is shown in FIG.
The “spherical silica particles” of the spherical silica abrasive grains B in Table 1 refer to spherical particles (generally commercially available colloidal silica) close to true spheres.
The particle size of the silica particles is a particle size obtained as an equivalent circle diameter measured within one particle in an electron microscope (TEM) observation image, that is, a major axis of an equivalent circle having the same area as the projected area of the particle. .

[Preparation of polishing liquid composition II used in step (3) (finish polishing)]
Polishing liquid composition II was prepared using the colloidal silica particle (abrasive grain f) of Table 1, sulfuric acid, hydrogen peroxide, and water. The content of each component in the polishing liquid composition II was colloidal silica particles: 5.0% by mass, sulfuric acid: 0.5% by mass, and hydrogen peroxide: 0.5% by mass. The pH of the polishing composition II was 1.4. Polishing liquid composition II was used in step (3) in the polishing of Examples 1 to 16, Reference Examples 1 to 9, and Comparative Examples 1 to 6.

2. Measuring method of each parameter [Volume average particle diameter (D1) and CV90 of abrasive grains a to k measured by dynamic light scattering method]
A standard sample was prepared by adding abrasive grains, sulfuric acid, and hydrogen peroxide to ion-exchanged water and mixing them. The contents of abrasive grains, sulfuric acid, and hydrogen peroxide in the standard sample are 0.1 to 5.0 mass%, 0.2 to 0.4 mass%, and 0.2 to 0.4 mass%, respectively. Adjustments were made as appropriate according to the type of silica abrasive used. The area of the scattering intensity distribution obtained by the Marquardt method at a detection angle of 90 ° when this standard sample is accumulated 200 times by the dynamic light scattering device DLS-6500 manufactured by Otsuka Electronics Co., Ltd. according to the instructions attached by the manufacturer. The particle size that was 50% of the total was determined and used as the volume average particle size (D1) of the silica particles. The CV value (CV90) of the silica particles at a detection angle of 90 ° was calculated as a value obtained by dividing the standard deviation in the scattering intensity distribution measured according to the above measurement method by the volume average particle diameter and multiplying by 100.

[ΔCV value]
In the same manner as the CV90 measurement method, the CV value (CV30) of the silica particles at a detection angle of 30 ° was measured, and a value obtained by subtracting CV90 from CV30 was obtained to obtain the ΔCV value of silica particles A or B.
(Measurement conditions for DLS-6500)
Detection angle 90 °
Sampling time: 2-10 (μm) as appropriate Correlation Channel: 256-512 (ch) as appropriate Correlation Method: TI
Sampling temperature: 25.0 ° C
Detection angle 30 °
Sampling time: Adjusted appropriately at 4-20 (μm) Correlation Channel: Adjusted appropriately at 512-2048 (ch) Correlation Method: TI
Sampling temperature: 25 ° C

[Measurement of specific surface area converted particle diameter (D2) of abrasive grains a to k by BET method]
The specific surface area of the abrasive grains is subjected to the following [pretreatment], and then approximately 0.1 g of a measurement sample is precisely weighed to 4 digits after the decimal point in a measurement cell, and immediately under the measurement at 110 ° C. for 30 minutes immediately before the measurement of the specific surface area. After drying, the surface area was measured by a nitrogen adsorption method (BET method) using a specific surface area measuring device (micromeritic automatic specific surface area measuring device “Flowsorb III2305” (manufactured by Shimadzu Corporation)).
[Preprocessing]
(A) The slurry-like abrasive grains are adjusted to pH 2.5 ± 0.1 with a nitric acid aqueous solution.
(B) The slurry-like abrasive grains adjusted to pH 2.5 ± 0.1 are placed in a petri dish and dried in a hot air dryer at 150 ° C. for 1 hour.
(C) After drying, the obtained sample is finely ground in an agate mortar.
(D) The pulverized sample is suspended in ion exchange water at 40 ° C. and filtered through a 1 μm membrane filter.
(E) The filtrate on the filter is thoroughly washed with 20 g of ion exchange water (40 ° C.).
(F) The filter to which the filtrate is attached is dried in an atmosphere of 110 ° C. for 4 hours.
(G) The dried filtrate was taken so that filter waste was not mixed and finely pulverized with a mortar to obtain a measurement sample.

[D10, D50, and D90 of silica abrasive grains]
A 1% by mass dispersion obtained by diluting the silica abrasive grains with ion-exchanged water was put into the following measuring apparatus to obtain a volume particle size distribution of the silica abrasive grains.
Measuring equipment: Malvern Zetasizer Nano “Nano S”
Measurement conditions: Sample volume 1.5 mL
: Laser He-Ne, 3.0 mW, 633 nm
: Scattered light detection angle 173 °
The particle sizes at which the cumulative volume frequency of the obtained volume particle size distribution becomes 10%, 50%, and 90% were defined as D10, D50 (volume average particle diameter), and D90, respectively.

[Total overlap frequency of volume particle size distribution of silica particles]
The volume particle size distribution of each of the silica particle components (abrasive grains a to k) was obtained by the same measurement method as that for silica abrasive grains D10, D50, and D90. In the combinations of abrasive grains used in Examples 1 to 16 and Reference Examples 3 to 9 (Table 2), the sum of the cumulative volume frequencies of the overlapping particle size range is the cumulative volume frequency of all silica particle components (200 for the two-component mixed system). In a three-component mixed system, a value obtained by dividing by 300) and multiplying by 100 was calculated as an overlap frequency [%]. FIG. 3 shows an example of a graph in which the volume particle size distributions of combinations of abrasive grains in Examples 8 to 11 are overlapped.

[Shape of silica abrasive grains]
Silica abrasive grains observed with a transmission electron microscope (TEM) manufactured by JEOL (trade name “JEM-2000FX”, 80 kV, 1 to 50,000 times) are taken as image data with a scanner on a personal computer, and analysis software “WinROOF ( Ver. 3.6) ”(distributor: Mitani Corporation), the shape of 1000 to 2000 silica particle data was observed.

[Measurement of average secondary particle diameter of abrasive grains]
An aqueous solution containing 0.5% by mass of Poise 530 (manufactured by Kao Corporation) was used as a dispersion medium and introduced into the following measuring apparatus, and then a sample was introduced so that the transmittance was 75 to 95%. After applying ultrasonic waves for a minute, the average secondary particle diameter of the abrasive grains was measured.
Measuring instrument: Laser diffraction / scattering particle size distribution measuring device LA920 manufactured by Horiba, Ltd.
Circulation strength: 4
Ultrasonic intensity: 4

3. Polishing conditions Polishing of the substrate to be polished was performed according to steps (1) to (3). The conditions for each step are shown below. Step (3) was performed with a polishing machine separate from the polishing machine used in step (1).
[Polished substrate]
The substrate to be polished was an aluminum alloy substrate plated with Ni—P. The substrate to be polished had a thickness of 1.27 mm and a diameter of 95 mm.

[Step (1): Rough polishing]
Polishing machine: Double-side polishing machine (9B-type double-side polishing machine, manufactured by Speed Fam Co., Ltd.)
Polishing liquid: Polishing liquid composition I
Polishing pad: Suede type (foam layer: polyurethane elastomer), thickness 0.82-1.26 mm, average pore diameter 20-30 μm, surface layer compression ratio: 2.5% (Filwel, manufactured by Fujibo)
Plate rotation speed: 35 rpm
Polishing load: 9.8 kPa (set value)
Polishing liquid supply amount: 100 mL / min (0.076 mL / (cm ² · min))
Polishing time: 5 minutes Polishing amount: 110 mg to 160 mg (per 95 mm diameter disc)
Number of substrates loaded: 10

[Step (2): Cleaning]
The substrate obtained in the step (1) was washed under the following conditions.
1. The substrate obtained in the step (1) is immersed for 5 minutes in a tank containing a pH 12 alkaline detergent composition made of 0.1 mass% KOH aqueous solution.
2. The substrate after immersion is rinsed with ion exchange water for 20 seconds.
3. The rinsed substrate is transferred to a scrub cleaning unit in which a cleaning brush is set and cleaned.

[Step (3): Final polishing]
Polishing machine: Double-side polishing machine (9B type double-side polishing machine, manufactured by Speedfam Co., Ltd.), polishing machine separate from the polishing machine used in step (1): Polishing liquid: Polishing liquid composition II
Polishing pad: Suede type (foam layer: polyurethane elastomer), thickness 0.9mm, average pore diameter 5μm, surface layer compressibility: 10.2% (Fujibo)
Plate rotation speed: 40 rpm
Polishing load: 9.8 kPa
Polishing liquid supply amount: 100 mL / min (0.076 mL / (cm ² · min))
Polishing time: 2 minutes Polishing amount: 0.04-0.10 mg / (cm ² · min)
Number of loaded substrates: 10 sheets After the step (3), cleaning was performed. The washing conditions were the same as in the above step (2).

4). Evaluation method [Measurement method and evaluation of polishing rate and polishing amount in step (1)]
Each substrate before and after polishing was weighed (measured by Sartorius, “BP-210S”) and introduced into the following formula to determine the polishing amount. The value was calculated. The results are shown in Table 2.
Weight loss (g) = {weight before polishing (g) −weight after polishing (g)}
Polishing amount (μm) = weight reduction amount (g) / substrate one side area (mm ² ) / 2 / Ni—P plating density (g / cm ³ ) × 10 ⁶
(The area on one side of the substrate is calculated as 6597 mm ² and Ni—P plating density 8.4 g / cm ³ )

[Method for Evaluating Long-Period Defect (PED) on Substrate Surface After Step (1)]
About both surfaces (20 points in total) of the 10 substrates after the polishing in the step (1), the occurrence rate (%) was determined under the following conditions. As shown in FIG. 4, when a small spot that can be confirmed on the substrate surface is PED, and even one point of PED can be visually confirmed on the substrate surface, the surface is regarded as having a long-period defect.
Long-period defect rate (%)
= (Number of substrate surfaces on which long-period defects are generated / 20) × 100
The long-period defect occurrence rate was evaluated in five stages according to the following criteria. That is, the larger the value, the lower the occurrence rate of long-period defects. The results are shown in Table 2.
[Evaluation criteria]
Long-period defect occurrence rate: Evaluation: 10% or less: 5 “Generation is extremely suppressed and improvement in substrate yield can be expected”
10% over 20%: 4 “actual production possible”
20% over 30%: 3 “Improvement is required for actual production”
30% over 50%: 2 “Substrate yield is greatly reduced”
50% or more: 1 “far from actual production (same level as when using ordinary silica abrasive grains)”
[measuring equipment]
Optical interference type surface profile measuring machine: OptiFLAT III (manufactured by KLA Tencor)
Radius Inside / Out: 14.87mm / 47.83mm
Center X / Y: 55.44mm / 53.38mm
Low Cutoff: 2.5mm
Inner Mask: 18.50mm, Outer Mask: 45.5mm
Long Period: 2.5mm, Wa Correction: 0.9, Rn Correction: 1.0
No Zernike Terms: 8

[Evaluation Method for Reduction Efficiency of Abrasive Solution Supply in Step (1)]
The polishing in the step (1) is performed at a polishing liquid supply amount of 100 mL / min (0.076 mL / (cm ² · min)). When the polishing liquid supply amount is separately reduced under the following conditions: Further, it was determined whether the decrease in the polishing rate can be suppressed within 10%. That is, if the decrease in the polishing rate can be suppressed within 10%, it is considered that the supply amount of the polishing liquid can be reduced without significantly impairing the productivity, which means that it is excellent from the viewpoint of economy.
Reduction in polishing rate (%)
= (Polishing speed under reduced polishing liquid supply rate) / (Polishing polishing liquid supply rate at 100 mL / min) × 100
Table 2 shows the results of the four-stage evaluation of the reduction efficiency of the polishing liquid supply amount based on the following criteria.
[Evaluation criteria]
Reduction efficiency of polishing liquid supply amount (relative value): Evaluation can be reduced by 30% (polishing rate decrease within 10% at 70 mL / min): A “Excellent economic efficiency”
Can be reduced by 20% (polishing rate is less than 10% at 80 mL / min): B “Excellent economy”
Can be reduced by 10% (90% / min. Polishing speed is less than 10%): C “Somewhat economical”
10% cannot be reduced (at 90 mL / min, the polishing rate decreases more than 10%): D “It is difficult to reduce the amount of polishing liquid supplied in actual production”

[Method for evaluating protrusion defect after step (3)]
Measuring instrument: OSA7100 (manufactured by KLA Tencor)
Evaluation: Polishing was performed using the polishing composition II, and then 4 pieces were selected at random, and each substrate was irradiated with a laser at 10,000 rpm to measure the number of abrasive sticks. Divide the total number of abrasive sticks (pieces) on both surfaces of each of the four substrates by 8 to obtain the number of abrasive sticks per board surface (number of protrusion defects) (relative value with Comparative Example 1 as 100). Was calculated. Table 2 shows the relative values of the number of protrusion defects and the results of evaluating the number of protrusion defects according to the following criteria.
[Evaluation criteria]
Number of protrusion defects (relative value): Evaluation Less than 95: A “Generation is extremely suppressed and an improvement in substrate yield can be expected”
95-110
110 to less than 125: C “Improvement is required for actual production”
125 or more: D “Substrate yield decreases significantly”

5. result

As shown in Table 2, in Examples 1 to 16, compared with Comparative Examples 1 to 6 and Reference Examples 1 to 9, the polishing rate of the rough polishing in the step (1) was not greatly impaired, and the step (3) The long-period defects (PED) after rough polishing in the step (1) could be reduced without deteriorating the number of protrusion defects on the substrate after final polishing.

Further, as shown in Table 2, in Examples 1 to 16, the amount of polishing liquid supplied in step (1) can be further reduced as compared with Comparative Examples 1 to 6 and Reference Examples 1 to 9.

According to the present disclosure, in one or a plurality of embodiments, long-period defects can be reduced while maintaining the polishing rate, so that the substrate yield can be improved while maintaining the productivity of manufacturing the magnetic disk substrate. In one or a plurality of embodiments, the present disclosure can be suitably used for manufacturing a magnetic disk substrate.

51 ... first polishing machine, 52 ... cleaning unit, 53 ... second polishing machine

Claims

(1) a step of polishing a surface to be polished of a substrate to be polished using the polishing liquid composition I;
(2) a step of cleaning the substrate obtained in step (1), and
(3) having a step of polishing the substrate obtained in the step (2) using a polishing liquid composition II containing silica particles C;
A method of manufacturing a magnetic disk substrate in which the steps (1) and (3) are performed by another polishing machine,
(I) The polishing liquid composition I in the step (1) contains non-spherical silica particles A, spherical silica particles B, an acid, an oxidizing agent, and water,
(Ii) In the polishing composition I in the step (1), the mass ratio (A / B) of the non-spherical silica particles A and the spherical silica particles B is 80/20 or more and 99/1 or less, and silica The total content of the non-spherical silica particles A and the spherical silica particles B with respect to the whole particles exceeds 98.0% by mass,
(Iii) The non-spherical silica particle A has a ΔCV value of more than 0.0% and less than 10%,
(Iv) The particle diameter ratio (D1 / D2) of the volume average particle diameter (D1) determined by the dynamic light scattering method and the specific surface area converted particle diameter (D2) determined by the BET method of the non-spherical silica particles A is 2.00 or more and 4 .00 or less,
(V) The volume average particle diameter (D1) of the spherical silica particles B by a dynamic light scattering method is 6.0 nm or more and 80.0 nm or less,
(Vi) The method for producing a magnetic disk substrate, wherein the acid is at least one selected from the group consisting of phosphoric acids, phosphonic acids, organic phosphonic acids, and combinations thereof.
The non-spherical silica particles A are at least one selected from the group consisting of confetti-type silica particles A1, deformed-type silica particles A2, deformed and confetti-type silica particles A3, and combinations thereof. 2. A method for producing a magnetic disk substrate according to 1.
3. The method of manufacturing a magnetic disk substrate according to claim 1, wherein CV90 of the non-spherical silica particles A is 20.0% or more and 40.0% or less.
The magnetic disk substrate according to any one of claims 1 to 3, wherein the spherical silica particles B have a ΔCV value of more than 0% and 10% or less, and a CV90 of 10.0% or more and 35.0% or less. Method.
5. The method of manufacturing a magnetic disk substrate according to claim 1, wherein a polishing amount per substrate to be polished in the step (1) is 110 mg or more and 160 mg or less.
6. The method for manufacturing a magnetic disk substrate according to claim 1, wherein the polishing liquid composition I does not substantially contain alumina abrasive grains.
The method for producing a magnetic disk substrate according to any one of claims 1 to 6, wherein the non-spherical silica particles A are silica particles produced by a water glass method.
The spherical silica particles B are two types of particles having different particle sizes,
The two types of particles are a combination of spherical particles of 6.0 nm to 15.0 nm and spherical particles of 15.5 nm to 70.0 nm, or spherical particles of 15.5 nm to 30.0 nm and 30. The method for manufacturing a magnetic disk substrate according to claim 1, wherein the magnetic disk substrate is a combination with spherical particles of 5 nm or more and 70.0 nm or less.
The magnetism according to any one of claims 1 to 8, wherein the total overlap frequency of the volume particle size distribution of the non-spherical silica particles A and the spherical silica particles B in the polishing liquid composition I is 0% or more and 50% or less. A manufacturing method of a disk substrate.
10. The method for producing a magnetic disk substrate according to claim 1, wherein the polishing composition I has a pH of 0.5 or more and 6.0 or less.
The method for manufacturing a magnetic disk substrate according to claim 1, wherein the substrate to be polished is a Ni—P plated aluminum alloy substrate.
A method for polishing a magnetic disk substrate, comprising steps (1) to (3) in the method for manufacturing a magnetic disk substrate according to any one of claims 1 to 11.
A first polishing machine for performing the polishing in step (1) in the method of manufacturing a magnetic disk substrate according to any one of claims 1 to 11,
A cleaning unit for performing the cleaning in the step (2) in the method of manufacturing a magnetic disk substrate according to any one of claims 1 to 11,
A magnetic disk substrate polishing system comprising: a second polishing machine that performs the polishing in step (3) in the method of manufacturing a magnetic disk substrate according to claim 1.
Containing abrasive grains, acid, oxidant and water,
The abrasive contains non-spherical silica particles A and spherical silica particles B,
The mass ratio A / B between the non-spherical silica particles A and the spherical silica particles B is 80/20 or more and 99/1 or less,
The non-spherical silica particle A has a ΔCV value of more than 0.0% and less than 10%,
CV90 of the non-spherical silica particles A is 20.0% or more and 40.0% or less,
The ΔCV value of the spherical silica particles B is higher than 0% and 10% or lower, and the CV90 of the spherical silica B is 10.0% or higher and 35.0% or lower,
The particle diameter ratio (D1 / D2) of the volume average particle diameter (D1) by the dynamic light scattering method of the non-spherical silica particles A to the specific surface area conversion particle diameter (D2) by the BET method is 2.00 or more and 4.00 or less. And
The volume average particle diameter D1 of the spherical silica particles B by a dynamic light scattering method is 6.0 nm or more and 80.0 nm or less,
A polishing composition for a magnetic disk substrate, wherein the acid is at least one selected from the group consisting of phosphoric acids, phosphonic acids, organic phosphonic acids, and combinations thereof.